How to make chainable function in JavaScript?

Question

Lets imagine function like this:

function foo(x) {
    x += \'+\';
    return x;
}

Usage of it would be like:

var x, y;
x =         


        

Answer 1

Sure, the trick is to return the object once you're done modifying it:

String.prototype.foo = function() {
    return this + "+";
}

var str = "Notepad";
console.log(str.foo().foo().toUpperCase());

http://jsfiddle.net/Xeon06/vyFek/

To make the method available on String, I'm modifying it's prototype. Be careful not to do this on Object though, as it can cause problems when enumerating over their properties.