exist-utils

This package is a collection of util functions that emulate CoffeeScript existence operator. While waiting that some of them are integrated in the next version of JavaScript, you can use this package while porting from CoffeeScript, etc.

Installation

Node Installation

npm install exist-utils

You can then ExistUtils = require('exist-utils') or import * as ExistUtils from 'exist-utils'.

Browser Installation

Use the minified UMD build in the dist folder: here. It exports a global window.ExistUtils when imported as a <script> tag.

Usage

Each function as a full name (i.e. exists) and a shorthand (i.e. ex), both are specified in the title of their description. You can check the equivalence with CoffeeScript operators in the following section.

exists (ex)

Example:

if (!exists(arg)) {
  error('missing arg');
}

This is the equivalent to CoffeeScript val?, it checks if a value "exists" (is neither null nor undefined).

existsChained (exc)

Example:

if (!existsChained(arg, 'callback')) {
  error('no callback specified');
}

This is the equivalent to CoffeeScript obj?.prop?, it checks if a whole chain "exists".

existsChainedValue (excv)

Example:

const callback = existsChainedValue(arg, 'callback');
if (!exists(callback)) {
  error('no callback specified');
  return;
}
callback();

This is the equivalent to CoffeeScript obj?.prop, it checks if a whole chain "exists" and returns the final value.

elvis (el)

Example:

val = elvis(arg, 42);

This is the equivalent to CoffeeScript val ? default and a safer version to val || default. It returns the second value if the first one doesn't "exist".

callsIfExist (fnex)

Example:

callsIfExist(func, 1, 2);

This is the equivalent to CoffeeScript func?(1, 2), it checks the existence of the function and calls it with the provided arguments.

callsIfExistObj (fnexo)

Example:

callsIfExistObj(obj, 'func', 1, 2);

This is the equivalent to CoffeeScript obj?.func?(1, 2), it checks the existence of the function and calls it with the provided arguments while providing the right value for this.

CoffeeScript equivalents

| CoffeeScript | exist-utils | exist-utils shorthand | |:-------------------------|:-----------------------------------|:---------------------------| | val? | exists(val) | ex(val) | | obj?.prop? | existsChained(obj, 'prop') | exc(obj, 'prop') | | obj?.prop | existsChainedValue(obj, 'prop') | excv(obj, 'prop') | | val = arg ? 3 | val = elvis(arg, 3) | val = el(arg, 3) | | func?(a, b) | callsIfExist(func, a, b) | fnex(func, a, b) | | obj.func?(a, b) | callsIfExistObj(obj, func, a, b) | fnexo(obj, func, a, b) |

License

MIT, Copyright (c) 2017-2020 Louis Brunner