Method to determine the type of an object.

[robertschaft]

During my search for a function that is able to tell me the type of an object, I came up with the following idea:
Every object has a constructor (I am not sure about this) obj.constructor.
You can convert the constructor to a string with obj.constructor.toString(). That returns something like "function Date() { [native code] }" for a Date.
To get the string "Date" I use a regex, but perhaps a combination with indexOf and substr perform better.

function typeOfObject(obj) {
    if (typeof(obj) != 'object') return typeof(obj);
    obj.constructor.toString().match(/^function (\w+)\s*\("/)[1];
}

For performance reasons, i store the regex in a static variable. But again, there could be a different implementation.

function typeOfObject(obj) {
    if (typeof(obj) != 'object') return typeof(obj);
    if (typeof(this.regex) == 'undefined' ) this.regex = new RegExp("^function (\\w+)\\s*\\(");
    return this.regex.exec(obj.constructor.toString())[1];
}

Perhaps this idea is useful for you.

[jed]

you don't need the RegExp, just obj.constructor.name.

[robertschaft]

Nice :)
According to Mozilla Developer .name is Non-Standard.

[ghost]

Unfortunately, both function decompilation and the name property of functions are non-standard. You can, however, check an object's internal [[Class]] name using Object#toString(). This works for all native JavaScript objects.

var toString = Object.prototype.toString;

toString.call([]); // => "[object Array]"
toString.call(/foo/); // => "[object RegExp]"
toString.call(5); // => "[object Number]"
toString.call(true); // => "[object Boolean]"
toString.call(function(){}); // => "[object Function]"
toString.call("string"); // => "[object String]"
toString.call(new Date()); // => "[object Date]"

[ghost]

This blog post explains in greater detail how Object#toString() works.