Simplest way to check the type of a variable in JavaScript

Question

function type(arg) {
    return Object.prototype.toString.call(arg).slice(8, -1).toLowerCase();
}

Is there any flaw in the above code to check the type?

What is wrong with typeof? developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — Aaron Digulla
– Aaron Digulla, Commented Oct 9, 2013 at 15:41
I’d say the main flaw in this approach is that you assume that the result of the toString method of any given object that you might pass into that function would be the exact same text in every given browser … — C3roe
– C3roe, Commented Oct 9, 2013 at 15:52

Brian · Accepted Answer · 2013-10-09 15:41:41Z

2

Really depends on what you want the function to return. There are slight differences between typeof and type().

> type('wat')
"string"
> typeof 'wat'
"string"
> type(window)
"global"
> typeof window
"object"
> type(document)
"htmldocument"
> typeof document
"object"

answered Oct 9, 2013 at 15:41

Brian

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2 Comments

Lix Over a year ago

Sorry - too quick to vote. Before your edit it really didn't look like an answer. Vote retracted.

Brian Over a year ago

No worries, shouldn't have typed the response, then Ctrl+A/V the console output. I'm not a smart man.

Nitish Kumar · Accepted Answer · 2013-10-09 15:41:50Z

-1

Yes. there is a keyword typeof

e.g

var abc = typeof variablename;

here abc will contain type of variable

answered Oct 9, 2013 at 15:41

Nitish Kumar

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