null-coalescing.js

Simulate null-coalescing operator like in php with a function

Installation

$ npm install --save null-coalescing
$ # or
$ npm install --save git+https://github.com/Purexo/null-coalescing.js.git # if you don't want depend to npm-registery

Usage

const $N = require('null-coalescing')

const bar = {
  anonymous: true
}
const object = {
  foo: {
    bar: 'baz'
  }
}
object[bar] = {
  baz: [
    {name: 'name'}
  ]
}

Signature of $N function :

function $N(object = undefined, evaluatedPath = '', defaultValue = undefined, bind = undefined) {}

Simple use-case :

$N(object, 'foo.bar') // 'baz'
// and with dirty path string
$N(object, '  foo.bar ') // 'baz' (It work)

$N(object, `['foo'].bar.length`) // 3

Use-case with default value :

$N(object, 'bar.foo', 'Oh No, a savage default value !!!') // 'Oh No, a savage default value !!!'

its roughly equivalent to object.bar.foo || 'Oh No, a savage default value !!!'
but without TypeError breaking your code ^^
it's more like

var value = 'Oh No, a savage default value !!!'
try { value = object.bar.foo || value }
catch (e) {}

Yeah value is OK (with so many unclear lines)

Let's magic enter in your heart !

Notice [bar] in 2nd argument and {bar} the last argument or in bind or first arg of call

$N(object, `[bar].baz.name`, 'default', {bar}) // 'name'
$N.bind({bar})(object, `[bar].baz.name`) // 'name'
$N.call({bar}, object, `[bar].baz.name` // 'name'
$N.call({bar}, object, `[bar].baz.name.notExistroperty` // undefined
// object[bar].baz.name || 'default' // but without TypeError throwed in your face <3

In truth there is no magic, just a trick with nodejs vm module, this code use vm.runInContext

NodeJs with module, require, and files are really separated, no possibility to get the context of caller, so you need use the bindArgs or bind this to $N function with needed var of your context you want access with evaluatedPath argument

Don't know why you could use like that, but it's possible

$N() // undefined
$N(undefined, 'foo.bar', 'default') // 'default'