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...
}

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answered Dec 23, 2010 at 22:01

Scott Mitchell

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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

Shurdoof

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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.