What are useful JavaScript methods that extends built-in objects? [closed]

Answer 1

There are a ton of String.prototype functions from James Padolsey

https://github.com/padolsey/string.prototype

These include:

• camelize
• contains
• count
• enclose
• extract
• forEach
• forEachWord
• linkify
• many
• randomize
• remove
• reverse
• shorten
• sort
• toDOM
• trim
• wrap

Answer 2

Date.toMidnight

Date.prototype.toMidnight = function(){ 
  this.setMinutes(0); 
  this.setSeconds(0); 
  this.setHours(0) 
}

Answer 3

This is a prototype function for capitalizing a string:

String.prototype.capitalize = function() {
    return this.charAt(0).toUpperCase() + this.slice(1);
}

Answer 4

Function.prototype.bind from the Prototype library.

Similar to call and apply but allows you to return a reference to a function that is called in a particular context instead of executing it immediately. Also allows you to curry parameters. It's so useful that it became a part of ECMAScript 5 and is already being implemented natively in browsers.

Function.prototype.bind = function() {
  var __method = this, args = Array.prototype.slice.call(arguments), object = args.shift();
  return function() {
    var local_args = args.concat(Array.prototype.slice.call(arguments));
    if (this !== window) local_args.push(this);
    return __method.apply(object, local_args);
  }
}

Answer 5

Use the prototype chain like this:

String.prototype.AddWorld = function() { return this+'World' }

"Hello ".AddWorld(); // returns the string "Hello World"

Answer 6

Array contains:

Array.prototype.contains = function(obj) {
    for (var i=0; i < this.length; i++) {
        if(this[i] === obj) return i;
    }
    return -1;
}

Usage:

var arr = [1, 2, 3];
alert(arr.contains(2));

This little helper function tells you if your array contains an object. If it does then the index of the object is returned, otherwise -1 is returned.

Free Friday afternoon tip: don't ever ever ever modify the Object prototype. That would be just asking for a whole world of pain - I learnt this the hard way :)