Extended Function Code for javascriptArray array objects _ javascript skills

We often add custom extension functions to the prototype of String, Function, and Array, such as removing String spaces and sorting arrays. Today we will focus on how to extend the Array object.

1. Extend it directly on Array. prototype

2. Use your own method to expand the array object

It is extended directly on Array. prototype and cannot be used directly on dom objects (for example, nodeList obtained by document. getElementsByTagName ('P );

For those with cleanliness, the original ecological environment is also broken :)

First, let's take a look at some methods of yui Operation Array. Here I have stripped and changed the source code.

The Code is as follows:

(Function (){
Var YArray;

YArray = function (o, idx, arraylike ){
Var t = (arraylike )? 2: YArray. test (o ),
L, a, start = idx | 0;
If (t ){
Try {
Return Array. prototype. slice. call (o, start); // use the native method of Array to convert aguments to JS Array
} Catch (e ){
A = [];
L = o. length;
For (; start A. push (o [start]);
}
Return;
}
} Else {
Return [o];
}

}

YArray. test = function (o ){
Var r = 0;
If (o & (typeof o = 'object' | typeof o = 'function ')){
If (Object. prototype. toString. call (o) = "[object Array]") {
R = 1;
} Else {
Try {
If ('length' in o )&&! O. tagName &&! O. alert &&! O. apply ){
R = 2;
}
} Catch (e ){}
}
}
Return r;
}

YArray. each = (Array. prototype. forEach )? // Check whether the browser supports this function. If yes, the native
Function (a, f, o ){
Array. prototype. forEach. call (a | [], f, o | Y );
Return YArray;
}:
Function (a, f, o ){
Var l = (a & a. length) | 0, I;
For (I = 0; I <l; I = I + 1 ){
F. call (o | Y, a [I], I, );
}
Return YArray;
};

YArray. hash = function (k, v ){
Var o ={}, l = k. length, vl = v & v. length, I;
For (I = 0; I If (k [I]) {
O [k [I] = (vl & vl> I )? V [I]: true;
}
}

Return o;
};

YArray. indexOf = (Array. prototype. indexOf )?
Function (a, val ){
Return Array. prototype. indexOf. call (a, val );
}:
Function (a, val ){
For (var I = 0; iif (a [I] = val ){
Return I;
}
}
Return-1; // The result is not found.
};

YArray. numericSort = function (a, B ){
Return (a-B); // sort from small to large, return (B-a); from large to small
};


YArray. some = (Array. prototype. some )?
Function (a, f, o ){
Return Array. prototype. some. call (a, f, o );
}:
Function (a, f, o ){
Var l = a. length, I;
For (I = 0; I If (f. call (o, a [I], I, )){
Return true;
}
}
Return false;
};

})();

Use the native method of Array to convert aguments to other methods of JS Array (Dom object is not allowed, only traversal is allowed)

The Code is as follows:

Array. apply (null, arguments );
[]. Slice. call (arguments, 0 );
[]. Splice. call (arguments, 0, arguments. length );
[]. Concat. apply ([], arguments );
...

The YArray function can operate not only array objects but also nodeList objects.
YArray (document. getElementsByTagName ("p "));
Traverse dom objects and assemble them into an array :)

The Code is as follows:

A = [];
L = o. length;
For (; start A. push (o [start]);
}
Return;

YArray. each
Traverses the array. If a function is input, callback is executed for each traversal.

The Code is as follows:

YArray. each ([1, 2, 3], function (item ){
Alert (item); // three executions, 1, 2, 3
});

YArray. hash
Arrays assembled into key-value pairs can be understood as a json object.
YArray. hash (["a", "B"], [1, 2]);

YArray. indexOf
Returns the index value of this value in the array (to search for a value ).

YArray. indexOf ([1, 2], 1)
YArray. numericSort
Sorts arrays from small to large.
[3, 1, 2]. sort (YArray. numericSort );
YArray. some
Does the element in the array pass the callBack processing? If yes, true is immediately returned. If none of them exist, false is returned.

The Code is as follows:

YArray. some ([3, 1, 2], function (el ){
Return el <4;
})

Let's take a look at the array extensions of javascript 1.6-1.8 and learn how to implement the same functions.
Every
Filter
ForEach
IndexOf
LastIndexOf
Map
Some
Reduce
ReduceRight

Array. prototype. every

The Code is as follows:

If (! Array. prototype. every)
{
Array. prototype. every = function (fun/*, thisp */)
{
Var len = this. length >>> 0;
If (typeof fun! = "Function ")
Throw new TypeError ();
Var thisp = arguments [1];
For (var I = 0; I <len; I ++)
{
If (I in this &&
! Fun. call (thisp, this [I], I, this ))
Return false;
}
Return true;
};
}

Does each element in the array pass the callBack processing? If yes, true is returned. If one is not, false is immediately returned.
This is similar to some functions of the YUI type we just mentioned: the function is opposite.

Array. prototype. filter

The Code is as follows:

Array. prototype. filter = function (block/*, thisp */) {// filter, easy to add and filter.
Var values = [];
Var thisp = arguments [1];
For (var I = 0; I <this. length; I ++)
If (block. call (thisp, this [I])
Values. push (this [I]);
Return values;
};

Usage

The Code is as follows:

Var val = numbers. filter (function (t ){
Return t <5;
})
Alert (val );

For forEach, indexOf, and some, refer to the above yui code and do not repeat it.
The lastIndexOf code is similar to the indexOf code, but the traversal starts from the end.

Next, let's talk about 'map'

The Code is as follows:

Array. prototype. map = function (fun/*, thisp */){
Var len = this. length >>> 0;
If (typeof fun! = "Function ")
Throw new TypeError ();
Var res = new Array (len );
Var thisp = arguments [1];
For (var I = 0; I <len; I ++ ){
If (I in this)
Res [I] = fun. call (thisp, this [I], I, this );
}
Return res;
};

Traverse the array, execute functions, and iterate the array. Each element is used as a parameter to execute the callBack method. The callBack method processes each element and returns an array after processing.
Var numbers = [1, 4, 9];
Var roots = numbers. map (function (a) {return a * 2 });

Array. prototype. reduce

The Code is as follows:

Array. prototype. reduce = function (fun/*, initial */){
Var len = this. length >>> 0;
If (typeof fun! = "Function ")
Throw new TypeError ();
If (len = 0 & arguments. length = 1)
Throw new TypeError ();
Var I = 0;
If (arguments. length> = 2 ){
Var rv = arguments [1];
} Else {
Do {
If (I in this ){
Rv = this [I ++];
Break;
}
If (++ I> = len)
Throw new TypeError ();
} While (true );
}
For (; I <len; I ++ ){
If (I in this)
Rv = fun. call (null, rv, this [I], I, this );
}
Return rv;
};

Let the array element call the given function in sequence and return a value. In other words, the returned value must be used for the given function.

Array. prototype. reduceRight
From right to left.

The Code is as follows:

Array. prototype. reduceRight = function (fun/*, initial */){
Var len = this. length >>> 0;
If (typeof fun! = "Function ")
Throw new TypeError ();
If (len = 0 & arguments. length = 1)
Throw new TypeError ();
Var I = len-1;
If (arguments. length> = 2 ){
Var rv = arguments [1];
} Else {
Do {
If (I in this ){
Rv = this [I --];
Break;
}
If (-- I <0)
Throw new TypeError ();
} While (true );
}
For (; I> = 0; I --){
If (I in this)
Rv = fun. call (null, rv, this [I], I, this );
}
Return rv;
};

In addition, all the methods used can be added to Array. prototype.
For example, the commonly used toString

The Code is as follows:

Array. prototype. toString = function (){
Return this. join ('');
};

You can also add toJson, uniq, compact, reverse, etc.
Array Extension is helpful for development :)