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

Answer 1

PHP.JS is a very nice effort to port most of PHP's functions to JavaScript. They currently have an extremely impressive list:

Online at: http://phpjs.org/functions/index

Answer 2

String Replace All :

String.prototype.replaceAll = function(search, replace)
{
    //if replace is not sent, return original string otherwise it will
    //replace search string with 'undefined'.
    if (replace === undefined) {
        return this.toString();
    }

    return this.replace(new RegExp('[' + search + ']', 'g'), replace);
};

var str = 'ABCADRAE';
alert(str.replaceAll('A','X')); // output : XBCXDRXE

Answer 3

Here's the nice extension for the Date object that allows you to format the date very easily. It uses PHP's date syntax so those familiar with PHP will get it in no time. Others have a huge list of possible switches on the site as well. Personally I haven't found easier way to format dates to various formats.

Date Format

Answer 4

There is a nice article at http://maiaco.com/articles/js/missingArrayFunctions.php describing six helpful functions to add to the Array prototype. The functions are linearSearch (same as indexOf given in another answer), binarySearch, retainAll, removeAll, unique, and addAll. The article also includes the JavaScript code for each of the six functions and example code showing how to use them.

Answer 5

String.format

String.prototype.format = function (values) {

    var regex = /\{([\w-]+)(?:\:([\w\.]*)(?:\((.*?)?\))?)?\}/g;

    var getValue = function (key) {
            if (values == null || typeof values === 'undefined') return null;

            var value = values[key];
            var type = typeof value;

            return type === 'string' || type === 'number' ? value : null;
        };

    return this.replace(regex, function (match) {
        //match will look like {sample-match}
        //key will be 'sample-match';
        var key = match.substr(1, match.length - 2);

        var value = getValue(key);

        return value != null ? value : match;
    });
};

Usage:

alert('Program: {key1} {key2}'.format({ 'key1' : 'Hello', 'key2' : 'World' })); //alerts Program: hello world

Answer 6

The various list manipulation prototypes are always great. Since you want only one per post, I'll just post foldl, which I discovered via SML (it "folds" the list, left to right, it has a counter part in foldr of course).

Array.prototype.foldl = function(fnc,start) {
    var a = start;
    for (var i = 0; i < this.length; i++) {
        a = fnc(this[i],a);
    }
    return a;
}

Some trivial examples could be:

var l = ["hello" , "world"];
l.foldl(function(i, acc) { return acc+" "+i; }, "") // => returns "hello world"

Sadly, the failure of standard DOM methods to return true arrays makes alot of these such methods rather useless. And if you're using a Lib of some sort, they often define methods like these already (map, filter, exists, etc).