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?

score 1 · Accepted Answer · edited May 23 '17 at 11:55

1

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

edited May 23 '17 at 11:55

Community

answered Dec 23 '10 at 22:01

Scott Mitchell

Is this how you do if it is not undefined? if (myVariable !== undefined) { // myVariable has not been assigned a value... } – sehummel Dec 23 '10 at 22:02
@shummel: Sure, that would work. You could also do: `if (!(myVariable === undefined)) { ... }` – Scott Mitchell Dec 23 '10 at 22:03

score 0 · Answer 2 · answered Dec 23 '10 at 22:02

0

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

answered Dec 23 '10 at 22:02

Shurdoof

this will return true also for non existing variables – Dr.Molle Dec 23 '10 at 22:05
Non-existing variables probably don't have a value. – ceejayoz Dec 23 '10 at 22:10
Non-existing variables don't exist, the question was about a given variable. – Dr.Molle Dec 24 '10 at 03:59

2 Answers2