ansaurus

Question

Answer 1

A:

if(variable == undefined) {

NicolasT 2010-08-23 17:36:39

Answer 2

+5 A:

if(typeof(variable) == 'undefined')

aadravid 2010-08-23 17:36:52

what is typeof?

chromedude 2010-08-23 17:37:51

You don’t need the parentheses as `typeof` is an operator and not a function.

Gumbo 2010-08-23 17:39:40

@chromedude See here: https://developer.mozilla.org/En/Core_JavaScript_1.5_Reference/Operators/Special_Operators/typeof_Operator

Tim Goodman 2010-08-23 17:41:05

ok thanks, makes sense now

chromedude 2010-08-23 17:49:24

ya you are right Gumbo... sorry about that :) was in a hurry when i answered :P

aadravid 2010-08-23 20:12:08

Answer 3

+1 A:

Use the typeof operator here, like this:

if(typeof variable == "undefined") {

Nick Craver 2010-08-23 17:37:03

Why would you add an extra call to `typeof` when simply checking `variable == undefined` works?

Justin Niessner 2010-08-23 17:42:36

@Justin - `undefined` may be redefined, for example: http://jsfiddle.net/nick_craver/gHjg5/

Nick Craver 2010-08-23 17:51:50

Answer 4

A:

The first one

if (variable == undefined) {}

o6tech 2010-08-23 17:37:13

Answer 5

+3 A:

if (typeof variable == 'undefined')

AJ 2010-08-23 17:37:25

How to create an if statement in javascript that will run if a variable is undefined?