Assign null to javascript var - ends up as String

Question

I have initialized my variable as the following:

var name = null;

If I check it's value like this it doesnt do anything:

if(name == null) {
    alert("Name = null");
}

But if I change the if-clause to that, it works:

if(name == "null") {
    alert("Name = null");
}

Happy for every help.

The behavior reported is incorrect. `null == "null"` is false. — user2864740, Sep 18 '14 at 19:12
Wow, that even works for type comparison. `if(name === 'null')` will also pass — Sterling Archer, Sep 18 '14 at 19:12
@user2864740 ... are you suggesting that it's ever ok to use loose equality? — m59, Sep 18 '14 at 19:19
@m59 When did I imply that? However, using `===` here has *nothing* to do with the problem as both `null == "null"` and `null === "null"` are false. — user2864740, Sep 18 '14 at 19:20
@m59 First, off I do not believe it is always better to use `===`. Secondly, as I have argued, that question does not apply here. — user2864740, Sep 18 '14 at 19:23
@user2864740 could you provide an example of when it's not better to use type comparison? — Sterling Archer, Sep 18 '14 at 20:04
possible duplicate of [Using the variable “name” doesn't work](http://stackoverflow.com/q/10523701/1048572) — Bergi, May 11 '16 at 02:37

p.s.w.g · Accepted Answer · 2014-09-19T05:40:53.323

It's likely that you're running this is in global scope, in which case name refers to the Window.name property. Assigning a value to this property automatically causes the value to be converted to a string, for example, try opening up your browser's console and typing this:

var name = 123;
alert(typeof name);

You'll most likely get an alert that reads string.

However, if you place this in an IIFE (and ensure that you have a var declaration), it behaves as expected:

(function() {
    var name = null;
    if(name == null) {
        alert("Name = null"); // shows alert
    }
})();

Assign null to javascript var - ends up as String

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