is there something like isset of php in javascript/jQuery? [duplicate]

Question

Is there something in javascript/jQuery to check whether variable is set/available or not? In php, we use isset($variable) to check something like this.

thanks.

Answer 1

Try this expression:

typeof(variable) != "undefined" && variable !== null 

This will be true if the variable is defined and not null, which is the equivalent of how PHP's isset works.

You can use it like this:

if(typeof(variable) != "undefined" && variable !== null) {     bla(); } 

Answer 2

JavaScript isset() on PHP JS

function isset () {     // discuss at: http://phpjs.org/functions/isset     // +   original by: Kevin van     Zonneveld (http://kevin.vanzonneveld.net)     // +   improved by: FremyCompany     // +   improved by: Onno Marsman     // +   improved by: Rafał Kukawski     // *     example 1: isset( undefined, true);     // *     returns 1: false     // *     example 2: isset( 'Kevin van Zonneveld' );     // *     returns 2: true     var a = arguments,         l = a.length,         i = 0,         undef;      if (l === 0) {         throw new Error('Empty isset');     }      while (i !== l) {         if (a[i] === undef || a[i] === null) {             return false;         }         i++;     }     return true; }