By: Tobias Günther

Tobias Günther — Fri, 25 Sep 2009 07:08:02 +0000

Hi Phil, related to that, you can look at my previous article on “Type Checking” (http://blog.puremedia-online.de/2009/08/20/javascript-summed-up-3-type-checking/) where ‘constructor’ is explained.

By: Phil Idem

Phil Idem — Thu, 24 Sep 2009 17:27:31 +0000

A better alternative to using typeof is to use the built-in “constructor” property. For example:
for ( prop in myObject ){
var property = myObject[prop];
if (property && property.constructor === Function) {
// …that’s a function
}
}

The “constructor” argument references the function that created the object.

function MyConstructor()
{
}

var obj = new MyConstructor();
alert(obj.constructor === MyConstructor); // true

Might be worth mentioning that you can check for property existence with one of these expressions:
myObject.myProperty !== undefined
myObject.myProperty === undefined

Don’t use this: typeof(myObject.myProperty) != “undefined”

Comments on: JavaScript summed up #8: Reflection

By: Tobias Günther

By: Phil Idem