Asynchronous flow control

The material in this post is heavily inspired by Mixu's Node.js Book.

At its core, JavaScript is designed to be non-blocking on the "main" thread, this is where views are rendered. You can imagine the importance of this in the browser. When the main thread becomes blocked it results in the infamous "freezing" that end users dread, and no other events can be dispatched resulting in the loss of data acquisition, for example.

This creates some unique constraints that only a functional style of programming can cure. This is where callbacks come in to the picture.

However, callbacks can become challenging to handle in more complicated procedures. This often results in "callback hell" where multiple nested functions with callbacks make the code more challenging to read, debug, organize, etc.

async1(function (input: anyinput, result1: anyresult1) {
  async2(function (result2: anyresult2) {
    async3(function (result3: anyresult3) {
      async4(function (result4: anyresult4) {
        async5(function (output: anyoutput) {
          // do something with output
        });
      });
    });
  });
});
JavaScript

Of course, in real life there would most likely be additional lines of code to handle result1, result2, etc., thus, the length and complexity of this issue usually results in code that looks much more messy than the example above.

This is where functions come in to great use. More complex operations are made up of many functions:

  1. initiator style / input
  2. middleware
  3. terminator

The "initiator style / input" is the first function in the sequence. This function will accept the original input, if any, for the operation. The operation is an executable series of functions, and the original input will primarily be:

  1. variables in a global environment
  2. direct invocation with or without arguments
  3. values obtained by file system or network requests

Network requests can be incoming requests initiated by a foreign network, by another application on the same network, or by the app itself on the same or foreign network.

A middleware function will return another function, and a terminator function will invoke the callback. The following illustrates the flow to network or file system requests. Here the latency is 0 because all these values are available in memory.

function function final(someInput: any, callback: any): voidfinal(someInput: anysomeInput, callback: anycallback) {
  callback: anycallback(`${someInput: anysomeInput} and terminated by executing callback `);
}

function function middleware(someInput: any, callback: any): voidmiddleware(someInput: anysomeInput, callback: anycallback) {
  return function final(someInput: any, callback: any): voidfinal(`${someInput: anysomeInput} touched by middleware `, callback: anycallback);
}

function function initiate(): voidinitiate() {
  const const someInput: "hello this is a function "someInput = 'hello this is a function ';
  function middleware(someInput: any, callback: any): voidmiddleware(const someInput: "hello this is a function "someInput, function (result: anyresult) {
    var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
@sincev0.1.100
log(result: anyresult);
    // requires callback to `return` result
  });
}

function initiate(): voidinitiate();
JavaScript

State management

Functions may or may not be state dependent. State dependency arises when the input or other variable of a function relies on an outside function.

In this way there are two primary strategies for state management:

  1. passing in variables directly to a function, and
  2. acquiring a variable value from a cache, session, file, database, network, or other outside source.

Note, I did not mention global variable. Managing state with global variables is often a sloppy anti-pattern that makes it difficult or impossible to guarantee state. Global variables in complex programs should be avoided when possible.

Control flow

If an object is available in memory, iteration is possible, and there will not be a change to control flow:

function function getSong(): stringgetSong() {
  let let _song: string_song = '';
  let let i: numberi = 100;
  for (let i: numberi; let i: numberi > 0; let i: numberi -= 1) {
    let _song: string_song += `${let i: numberi} beers on the wall, you take one down and pass it around, ${
      let i: numberi - 1
    } bottles of beer on the wall\n`;
    if (let i: numberi === 1) {
      let _song: string_song += "Hey let's get some more beer";
    }
  }

  return let _song: string_song;
}

function function singSong(_song: any): voidsingSong(_song: any_song) {
  if (!_song: any_song) {
    throw new 
var Error: ErrorConstructor
new (message?: string, options?: ErrorOptions) => Error (+1 overload)
Error("song is '' empty, FEED ME A SONG!");
  }

  var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
@sincev0.1.100
log(_song: any_song);
}

const const song: stringsong = function getSong(): stringgetSong();
// this will work
function singSong(_song: any): voidsingSong(const song: stringsong);
JavaScript

However, if the data exists outside of memory the iteration will no longer work:

function function getSong(): stringgetSong() {
  let let _song: string_song = '';
  let let i: numberi = 100;
  for (let i: numberi; let i: numberi > 0; let i: numberi -= 1) {
    function setTimeout<[]>(callback: () => void, delay?: number): NodeJS.Timeout (+2 overloads)
Schedules execution of a one-time `callback` after `delay` milliseconds.

The `callback` will likely not be invoked in precisely `delay` milliseconds.
Node.js makes no guarantees about the exact timing of when callbacks will fire,
nor of their ordering. The callback will be called as close as possible to the
time specified.

When `delay` is larger than `2147483647` or less than `1` or `NaN`, the `delay`
will be set to `1`. Non-integer delays are truncated to an integer.

If `callback` is not a function, a `TypeError` will be thrown.

This method has a custom variant for promises that is available using
`timersPromises.setTimeout()`.
@sincev0.0.1@paramcallback The function to call when the timer elapses.@paramdelay The number of milliseconds to wait before calling the
`callback`. **Default:** `1`.@paramargs Optional arguments to pass when the `callback` is called.@returnsfor use with `clearTimeout()`
setTimeout(function () {
      let _song: string_song += `${let i: numberi} beers on the wall, you take one down and pass it around, ${
        let i: numberi - 1
      } bottles of beer on the wall\n`;
      if (let i: numberi === 1) {
        let _song: string_song += "Hey let's get some more beer";
      }
    }, 0);
  }

  return let _song: string_song;
}

function function singSong(_song: any): voidsingSong(_song: any_song) {
  if (!_song: any_song) {
    throw new 
var Error: ErrorConstructor
new (message?: string, options?: ErrorOptions) => Error (+1 overload)
Error("song is '' empty, FEED ME A SONG!");
  }

  var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
@sincev0.1.100
log(_song: any_song);
}

const const song: stringsong = function getSong(): stringgetSong('beer');
// this will not work
function singSong(_song: any): voidsingSong(const song: stringsong);
// Uncaught Error: song is '' empty, FEED ME A SONG!
JavaScript

Why did this happen? setTimeout instructs the CPU to store the instructions elsewhere on the bus, and instructs that the data is scheduled for pickup at a later time. Thousands of CPU cycles pass before the function hits again at the 0 millisecond mark, the CPU fetches the instructions from the bus and executes them. The only problem is that song ('') was returned thousands of cycles prior.

The same situation arises in dealing with file systems and network requests. The main thread simply cannot be blocked for an indeterminate period of time-- therefore, we use callbacks to schedule the execution of code in time in a controlled manner.

You will be able to perform almost all of your operations with the following 3 patterns:

  1. In series: functions will be executed in a strict sequential order, this one is most similar to for loops.
// operations defined elsewhere and ready to execute
const 
const operations: {
    func: any;
    args: any;
}[]
operations = [
  { func: anyfunc: function1, args: anyargs: args1 },
  { func: anyfunc: function2, args: anyargs: args2 },
  { func: anyfunc: function3, args: anyargs: args3 },
];

function function executeFunctionWithArgs(operation: any, callback: any): voidexecuteFunctionWithArgs(operation: anyoperation, callback: anycallback) {
  // executes function
  const { const args: anyargs, const func: anyfunc } = operation: anyoperation;
  const func: anyfunc(const args: anyargs, callback: anycallback);
}

function function serialProcedure(operation: any): voidserialProcedure(operation: anyoperation) {
  if (!operation: anyoperation) {
    var process: NodeJS.Processprocess.NodeJS.Process.exit(code?: number | string | null | undefined): never
The `process.exit()` method instructs Node.js to terminate the process
synchronously with an exit status of `code`. If `code` is omitted, exit uses
either the 'success' code `0` or the value of `process.exitCode` if it has been
set. Node.js will not terminate until all the `'exit'` event listeners are
called.

To exit with a 'failure' code:

```js
import { exit } from 'node:process';

exit(1);
```

The shell that executed Node.js should see the exit code as `1`.

Calling `process.exit()` will force the process to exit as quickly as possible
even if there are still asynchronous operations pending that have not yet
completed fully, including I/O operations to `process.stdout` and `process.stderr`.

In most situations, it is not actually necessary to call `process.exit()` explicitly. The Node.js process will exit on its own _if there is no additional_
_work pending_ in the event loop. The `process.exitCode` property can be set to
tell the process which exit code to use when the process exits gracefully.

For instance, the following example illustrates a _misuse_ of the `process.exit()` method that could lead to data printed to stdout being
truncated and lost:

```js
import { exit } from 'node:process';

// This is an example of what *not* to do:
if (someConditionNotMet()) {
  printUsageToStdout();
  exit(1);
}
```

The reason this is problematic is because writes to `process.stdout` in Node.js
are sometimes _asynchronous_ and may occur over multiple ticks of the Node.js
event loop. Calling `process.exit()`, however, forces the process to exit _before_ those additional writes to `stdout` can be performed.

Rather than calling `process.exit()` directly, the code _should_ set the `process.exitCode` and allow the process to exit naturally by avoiding
scheduling any additional work for the event loop:

```js
import process from 'node:process';

// How to properly set the exit code while letting
// the process exit gracefully.
if (someConditionNotMet()) {
  printUsageToStdout();
  process.exitCode = 1;
}
```

If it is necessary to terminate the Node.js process due to an error condition,
throwing an _uncaught_ error and allowing the process to terminate accordingly
is safer than calling `process.exit()`.

In `Worker` threads, this function stops the current thread rather
than the current process.
@sincev0.1.13@paramcode The exit code. For string type, only integer strings (e.g.,'1') are allowed.
exit(0); // finished
  }

  function executeFunctionWithArgs(operation: any, callback: any): voidexecuteFunctionWithArgs(operation: anyoperation, function (result: anyresult) {
    // continue AFTER callback
    function serialProcedure(operation: any): voidserialProcedure(
const operations: {
    func: any;
    args: any;
}[]
operations.
Array<{ func: any; args: any; }>.shift(): {
    func: any;
    args: any;
} | undefined
Removes the first element from an array and returns it.
If the array is empty, undefined is returned and the array is not modified.
shift());
  });
}

function serialProcedure(operation: any): voidserialProcedure(
const operations: {
    func: any;
    args: any;
}[]
operations.
Array<{ func: any; args: any; }>.shift(): {
    func: any;
    args: any;
} | undefined
Removes the first element from an array and returns it.
If the array is empty, undefined is returned and the array is not modified.
shift());
JavaScript
  1. Limited in series: functions will be executed in a strict sequential order, but with a limit on the number of executions. Useful when you need to process a large list but with a cap on the number of items successfully processed.
let let successCount: numbersuccessCount = 0;

function function final(): voidfinal() {
  var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
@sincev0.1.100
log(`dispatched ${let successCount: numbersuccessCount} emails`);
  var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
@sincev0.1.100
log('finished');
}

function function dispatch(recipient: any, callback: any): voiddispatch(recipient: anyrecipient, callback: anycallback) {
  // `sendMail` is a hypothetical SMTP client
  sendMail(
    {
      subject: stringsubject: 'Dinner tonight',
      message: stringmessage: 'We have lots of cabbage on the plate. You coming?',
      smtp: anysmtp: recipient: anyrecipient.email,
    },
    callback: anycallback
  );
}

function function sendOneMillionEmailsOnly(): voidsendOneMillionEmailsOnly() {
  getListOfTenMillionGreatEmails(function (err: anyerr, bigList: anybigList) {
    if (err: anyerr) {
      throw err: anyerr;
    }

    function function (local function) serial(recipient: any): voidserial(recipient: anyrecipient) {
      if (!recipient: anyrecipient || let successCount: numbersuccessCount >= 1000000) {
        return function final(): voidfinal();
      }

      function dispatch(recipient: any, callback: any): voiddispatch(recipient: anyrecipient, function (_err: any_err) {
        if (!_err: any_err) {
          let successCount: numbersuccessCount += 1;
        }

        function (local function) serial(recipient: any): voidserial(bigList: anybigList.pop());
      });
    }

    function (local function) serial(recipient: any): voidserial(bigList: anybigList.pop());
  });
}

function sendOneMillionEmailsOnly(): voidsendOneMillionEmailsOnly();
JavaScript
  1. Full parallel: when ordering is not an issue, such as emailing a list of 1,000,000 email recipients.
let let count: numbercount = 0;
let let success: numbersuccess = 0;
const const failed: any[]failed = [];
const 
const recipients: {
    name: string;
    email: string;
}[]
recipients = [
  { name: stringname: 'Bart', email: stringemail: 'bart@tld' },
  { name: stringname: 'Marge', email: stringemail: 'marge@tld' },
  { name: stringname: 'Homer', email: stringemail: 'homer@tld' },
  { name: stringname: 'Lisa', email: stringemail: 'lisa@tld' },
  { name: stringname: 'Maggie', email: stringemail: 'maggie@tld' },
];

function function dispatch(recipient: any, callback: any): voiddispatch(recipient: anyrecipient, callback: anycallback) {
  // `sendMail` is a hypothetical SMTP client
  sendMail(
    {
      subject: stringsubject: 'Dinner tonight',
      message: stringmessage: 'We have lots of cabbage on the plate. You coming?',
      smtp: anysmtp: recipient: anyrecipient.email,
    },
    callback: anycallback
  );
}

function function final(result: any): voidfinal(result: anyresult) {
  var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
@sincev0.1.100
log(`Result: ${result: anyresult.count} attempts \
      & ${result: anyresult.success} succeeded emails`);
  if (result: anyresult.failed.length) {
    var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
@sincev0.1.100
log(`Failed to send to: \
        \n${result: anyresult.failed.join('\n')}\n`);
  }
}


const recipients: {
    name: string;
    email: string;
}[]
recipients.
Array<{ name: string; email: string; }>.forEach(callbackfn: (value: {
    name: string;
    email: string;
}, index: number, array: {
    name: string;
    email: string;
}[]) => void, thisArg?: any): void
Performs the specified action for each element in an array.
@paramcallbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.@paramthisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach(function (
recipient: {
    name: string;
    email: string;
}
recipient) {
  function dispatch(recipient: any, callback: any): voiddispatch(
recipient: {
    name: string;
    email: string;
}
recipient, function (err: anyerr) {
    if (!err: anyerr) {
      let success: numbersuccess += 1;
    } else {
      const failed: any[]failed.Array<any>.push(...items: any[]): number
Appends new elements to the end of an array, and returns the new length of the array.
@paramitems New elements to add to the array.
push(
recipient: {
    name: string;
    email: string;
}
recipient.name: stringname);
    }
    let count: numbercount += 1;

    if (let count: numbercount === 
const recipients: {
    name: string;
    email: string;
}[]
recipients.Array<{ name: string; email: string; }>.length: number
Gets or sets the length of the array. This is a number one higher than the highest index in the array.
length) {
      function final(result: any): voidfinal({
        count: numbercount,
        success: numbersuccess,
        failed: any[]failed,
      });
    }
  });
});
JavaScript

Each has its own use cases, benefits, and issues you can experiment and read about in more detail. Most importantly, remember to modularize your operations and use callbacks! If you feel any doubt, treat everything as if it were middleware!

ÎnapoiPublicarea unui pachet TypeScriptÎnaintePrezentare generală a operațiunilor blocante vs non-blocante
Durată de citire
6 min.
Autori
ACW
Contribuie
Editează această pagină
Cuprins
  1. State management
  2. Control flow