Question

15

typeof for RegExp

rated 0 times [ 16] [ 1] / answers: 1 / hits: 53552 / 14 Years ago, thu, december 2, 2010, 12:00:00

Is there anyway to detect if a JavaScript object is a regex?

For example, I would like to do something like this:

var t = /^foo(bar)?$/i;

alert(typeof t); //I want this to return regexp

Is this possible?

Thanks!

EDIT: Thanks for all the answers. It seems I have two very good choices:

obj.constructor.name === RegExp

or

obj instanceof RegExp

Any major pros/cons to either method?

Thanks again!

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kaitlynd

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answered 14 Years ago juand · Accepted Answer

You can use instanceof operator:

var t = /^foo(bar)?$/i;

alert(t instanceof RegExp);//returns true

In fact, that is almost the same as:

var t = /^foo(bar)?$/i;

alert(t.constructor == RegExp);//returns true

Keep in mind that as RegExp is not a primitive data type, it is not possible to use typeof operator which could be the best option for this question.

But you can use this trick above or others like duck type checking, for example, checking if such object has any vital methods or properties, or by its internal class value (by using {}.toString.call(instaceOfMyObject)).