sixpaq / jsutils

A library with frequently used functions to simplify asynchronous processes

Array extensions

firstOrNull

This method is added to the Array prototype. This returns the first element of an array or null if the array is empty.

Examples:

const myArray = [1, 2, 3];
console.log(myArray.firstOrNull()); // returns 1

const myArray = [];
console.log(myArray.firstOrNull()); // returns null;

lastOrNull

This method is added to the Array prototype. This returns the last element of an array or null if the array is empty.

Examples:

const myArray = [1, 2, 3];
console.log(myArray.lastOrNull()); // returns 3

const myArray = [];
console.log(myArray.lastOrNull()); // returns null;

Future

This is a simple Future implementation based on deasync. This is an easy way to turn an asynchronous process in to a synchronous process.

Example:

const f = new Future();

setTimeout(() => {
  if (somethingBadHappened) {
    f.throw(new Error('Bad'));
  }
  f.return(5);
}, 2000);

// Here we wait for the result (5), which will be placed in the output or an exception is thown.
const output = f.wait;

parallel

Processes a list of functions in parallel and calls the callback when all functions have finished or when an error occures.

Syntax:

parallel(tasks, max = -1, callback);

Example:

const tasks = [];
tasks.push((cb) => {
  // do something
  cb(null, 5);
});

tasks.push((cb) => {
  // do something
  cb(null, 3);
});

parallel(tasks, (err, 5, results) => {
  // contains is now [5, 3] unless an error occured.
});

series

Processes a list of functions serial and calls the callback when all functions have finished or when an error occures.

Syntax:

series(tasks, callback);

Example:

const tasks = [];
tasks.push((cb) => {
  // do something
  cb(null, 5);
});

tasks.push((cb) => {
  // do something
  cb(null, 3);
});

series(tasks, (err, results) => {
  // contains is now [5, 3] unless an error occured.
});