A simple implementation of each () method in JavaScript

Each () is used to iterate through each element and make the appropriate processing, the following is a simple implementation:

Method One (direct function call):

The code is as follows

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function each (OBJ,FN) { if (!FN) return; if (obj instanceof array) {//array var i = 0, len = obj.length; for (; i<len;i++) { This in the IF (Fn.call (obj[i],i) = = false)//function points to obj[i],i as an index Break } }else if (typeof obj = = ' object ') {//objects var j = null; For (j in obj) { This in the IF (Fn.call (obj[j],j) = = false)//function points to obj[j],j as the property name Break } } } Call Method: var arry = [1,2,3,4,5,6,7]; var user = {name: ' Read on the Triangle Lake ', site: ' Http://www.111cn.net ', addr: ' Wuhan, Hubei ', _salary: ' 1w ', age:22}; Console.log (' ===function=== '); Each (arry,function (index) {//output array of the first five digits if (Index > 4) return false; Console.log (index+ ' => ' +this); }); Each (user,function (key) {//Output Public property/Method (a property or method that starts with the Convention "_" is private) if (!/^_/.test (key)) { if (typeof this = = ' function ') { Console.log (key+ ' => function [function] '); }else{ Console.log (key+ ' => ' +this); } } }); Execution results: ===function=== 0 => 1 1 => 2 2 => 3 3 => 4 4 => 5 Name => on the Lake Delta Site => http://www.111cn.net Addr => Hubei Wuhan Age => 22 Each => function [function]

Method two (prototype extension):

The code is as follows

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function _each (FN) { if (!FN) return; If (this instanceof array) {//array var i = 0, len = this.length; for (; i<len;i++) { This in the IF (Fn.call (this[i],i) = = false)//function points to obj[i],i as an index Break } }else if (typeof this = = ' object ') {//objects var j = null; For (J. This) { This in the IF (Fn.call (this[j],j) = = false)//function points to obj[j],j as the property name break; } } } Array.prototype.each = Object.prototype.each =_each;

Call Method:

code is as follows

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Console.log (' ===array.prototype| object.prototype=== '); Arry.each (function (index) {//output array of the first five digits if (Index > 4) return false; Console.log (index+ ' => ' +this); }); User.each (function (key) {//Output Public property/Method (a property or method that starts with the Convention "_" is private) if (!/^_/.test (key)) { if (typeof this = = ' function ') { Console.log (key+ ' => function [function] '); }else{ Console.log (key+ ' => ' +this); } } }); Execution results: ===array.prototype| object.prototype=== 0 => 1 1 => 2 2 => 3 3 => 4 4 => 5 Name => on the Lake Delta Site => http://www.111cn.net Addr => Hubei Wuhan Age => 22 Each => function [function]

And finally, I'm going to give you a little bit of justice. In fact, we can use jquery directly to help us complete, do not need to write so much code, such as

Each process one-dimensional array

The code is as follows	Copy Code
var arr1 = ["AAA", "BBB", "CCC"]; $.each (arr1, function (i,val) { alert (i); Alert (val); }); alert (i) outputs the 0,1,2 Alert (val) outputs the AAA,BBB,CCC

Each process two-dimensional array

The code is as follows	Copy Code
var arr2 = [[' A ', ' AA ', ' aaa '], [' B ', ' BB ', ' BBB '], [' C ', ' cc ', ' CCC ']] $.each (arr, function (I, item) { alert (i); alert (item); });

ARR2 is a two-dimensional array, the item is equivalent to taking each of the arrays in the two-dimensional array.
Item[0] Relative to the first value in each one-dimensional array
Alert (i) will output as 0,1,2 because the two-dimensional array contains 3 array elements
Alert (item) will output as [' a ', ' AA ', ' aaa '],[' b ', ' BB ', ' BBB '],[' C ', ' cc ', ' CCC ']

After a slight change to the processing of this two-bit array

code is as follows	copy code
var arr = [[' A ', ' AA ', ' aaa '], [' B ', ' BB ', ' BBB '], [' C ', ' cc ', ' CCC ']]        $.each (arr, functi On (i, item) {            $.each (item,function (j,val) {        alert (j);         alert (val);    }); });

Alert (j) will output as 0,1,2,0,1,2,0,1,2
Alert (val) will output as A,AA,AAA,B,BB,BBB,C,CC,CCC


Each process JSON data, which is more powerful and can loop through each attribute

The code is as follows	Copy Code
var obj = {one:1, two:2, three:3}; Each (obj, function (key, Val) { alert (key); Alert (val); });

Here alert (key) will output one two three
Alert (val) outputs the one,1,two,2,three,3
Here's why key is not a number but a property, because the JSON format is a set of unordered attributes-values, since the disorder, how to figure it.
And this val is equivalent to Obj[key]

It's easy to use and jquery is a lot more compatible.