Question

the question is straight forward. Just like in PHP we have the magic function __construct(), is there any related function or hack I can use in javascript?

Example:

function setLength() {
    /* Some work */
}

var a = new Object();
b = new String("Hello");
//Is there anyway the function setLength() will automatically be fired when an Object or String... created?

I’m looking forward to your answers. Thank a lot for any help.

[x]

Answer 1

Trying to overload String would be a bad idea, especially if working with third party libraries. Same would go for augmenting Object.

However, here is how you may do it, but I don’t recommend it..

var _String = String;

window.String = function() {
        setLength();
        return new _String(arguments[0]);
}

This obviously won’t be called when creating a primitive string too.

jsFiddle.

---

You could use a string factory function that returns a new String object and calls your function.

var stringFactory = function(chars) {
    setLength();
    return new String(chars);  
}

This has some advantages, mainly the String constructor is not overloaded.