Checking to see if a value exists in Javascript

Question

How do I check if a given variable has a value? What is the JS equivalent of PHP's isset?

Community · Accepted Answer · 2017-05-23 11:55:28Z

1

if (myVariable === undefined) { // myVariable has not been assigned a value... }

11 silver badge

answered Dec 23, 2010 at 22:01

8,7594 gold badges57 silver badges73 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Is this how you do if it is not undefined? if (myVariable !== undefined) { // myVariable has not been assigned a value... }

@shummel: Sure, that would work. You could also do: if (!(myVariable === undefined)) { ... }

Shurdoof · Accepted Answer · 2010-12-23 22:02:55Z

0

if(typeof variable === "undefined") { //code here }

answered Dec 23, 2010 at 22:02

1,71913 silver badges16 bronze badges

this will return true also for non existing variables

Non-existing variables probably don't have a value.

Non-existing variables don't exist, the question was about a given variable.