Dealing with Null in javascript

Question

I'm facing some difficulty when dealing with null values in JavaScript. I have two cases in my JavaScript where the object can be null or can have some other value so I do this:

if(feild_values != null || typeof(feild_values) != 'null') {
    alert(feild_values.id[i-1]);
}

However, Firebug gives me an error saying:

TypeError: feild_values is null alert(feild_values.id[i-1]);

How do I manage this?

@arxanas - Indeed, I hope that is an error that will not propagate through a large project. People need to realize how confusing spelling errors can be, especially in a dynamic language like JavaScript. — ChaosPandion
– ChaosPandion, Commented Aug 18, 2012 at 5:19

Steve Bazyl · Accepted Answer · 2012-08-18 05:08:57Z

4

Remove || typeof(feild_values) != 'null'

You don't need it and typeof(null) isn't 'null', its 'object'

Can simplify to:

if (feild_values) {
 ...
}

answered Aug 18, 2012 at 5:08

Steve Bazyl

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3 Comments

Antimony Over a year ago

Also, you should use the !== operator.

ChaosPandion Over a year ago

I'm not sure that this is the best replacement. The code path will fail if feild_values is non-empty string or even Boolean true.

tadman Over a year ago

That's for sure, but if your data isn't the right type, you've got a bug somewhere else. There's no need to be paranoid and write super defensive code that hides bugs.

Yevgeny Simkin · Accepted Answer · 2012-08-18 05:12:00Z

0

you should also be looking for typeof yourVar == "undefined"

answered Aug 18, 2012 at 5:12

Yevgeny Simkin

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