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Detecting an undefined object property in JavaScript

Would it be like this?

if(variable == undefined) {

or would it be like this?

if(variable == "undefined") {
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5 Answers 5

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if (typeof variable == 'undefined')
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if(typeof(variable) == 'undefined')
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You don’t need the parentheses as typeof is an operator and not a function.
@chromedude See here: developer.mozilla.org/En/Core_JavaScript_1.5_Reference/…
ya you are right Gumbo... sorry about that :) was in a hurry when i answered :P
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Use the typeof operator here, like this:

if(typeof variable == "undefined") {
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Why would you add an extra call to typeof when simply checking variable == undefined works?
@Justin - undefined may be redefined, for example: jsfiddle.net/nick_craver/gHjg5
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if(variable == undefined) {
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The first one

if (variable == undefined) {}
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