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

Answer 1

These two are wrappers for inserting and deleting elements from a particular position in an Array because I don't like the name splice.

// insert element at index
Array.prototype.insertAt = function(element, index) {
    this.splice(index, 0, element);
}

// delete element from index
Array.prototype.removeAt = function(index) {
    this.splice(index, 1);
}

Some more useful Array methods to get away from using indexes:

Array.prototype.first = function() {
    return this[0] || undefined;
};

Array.prototype.last = function() {
    if(this.length > 0) {
        return this[this.length - 1];
    }
    return undefined;
};

Array.prototype.max = function(array){
    return Math.max.apply(Math, array);
};

Array.prototype.min = function(array){
    return Math.min.apply(Math, array);
};

Some useful functions from the MooTools library:

Function.delay

Used to execute a function after the given milliseconds have elapsed.

// alerts "hello" after 2 seconds.
(function() {
    alert("hello");
}).delay(2000);    ​

Number.times

Similar to Ruby's times method for numbers, this accepts a function and executes it N times where N is the numbers value.

// logs hello 5 times
(5).times(function() {
    console.log("hello");
});

Answer 2

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

Usage:

var list = ["my", "array", "contents"];
alert(list.indexOf("contents"));     // outputs 2

Answer 3

String Padding :

String.prototype.padLeft = function (length, character) { 
     return new Array(length - this.length + 1).join(character || ' ') + this; 
}
'trial'.padLeft(7, 'X'); // output : 'XXtrial'
'trial'.padLeft(7);      // output : '  trial'



String.prototype.padRight = function (length, character) { 
     return this + new Array(length - this.length + 1).join(character || ' '); 
}
'trial'.padRight(7, 'X'); // output : 'trialXX'
'trial'.padRight(7);      // output : 'trial  '