PHP's isset in JavaScript

Here’s what our current JavaScript equivalent to PHP's isset looks like.

module.exports = functionisset () {
//  discuss at: https://locutus.io/php/isset/
// original by: Kevin van Zonneveld (https://kvz.io)
// improved by: FremyCompany
// improved by: Onno Marsman (https://twitter.com/onnomarsman)
// improved by: Rafał Kukawski (https://blog.kukawski.pl)
//   example 1: isset( undefined, true)
//   returns 1: false
//   example 2: isset( 'Kevin van Zonneveld' )
//   returns 2: true
const a = arguments
const l = a.length
let i = 0
let undef
if (l === 0) {
thrownewError('Empty isset')
  }
while (i !== l) {
if (a[i] === undef || a[i] === null) {
returnfalse
    }
    i++
  }
returntrue
}

How to use

You you can install via npm install locutus and require it via require('locutus/php/var/isset'). You could also require the var module in full so that you could access var.isset instead.

If you intend to target the browser, you can then use a module bundler such as Parcel, webpack, Browserify, or rollup.js. This can be important because Locutus allows modern JavaScript in the source files, meaning it may not work in all browsers without a build/transpile step. Locutus does transpile all functions to ES5 before publishing to npm.

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we don't consider it to be a bad thing that many of our functions are first iterations, which may still have their fair share of issues. We hope that these flaws will inspire others to come up with better ideas.

This way of working also means that we don't offer any production guarantees, and recommend to use Locutus inspiration and learning purposes only.

Examples

Please note that these examples are distilled from test cases that automatically verify our functions still work correctly. This could explain some quirky ones.

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