How to Implement JavaScript Array Iteration

This article mainly introduces the JavaScript array iteration method, which has good reference value. Next, let's take a look at it. This article mainly introduces the JavaScript array iteration method, which has good reference value. Let's take a look at it with the small Editor.

Data processing is often involved in recent work. arrays are especially common and often need to be traversed and converted. Online articles are scattered, so you have to find out the red books to read them, by the way, it is easy to query later.

Common array Iteration Methods

ECMAScript5 defines five Iteration Methods for arrays. Each method accepts two parameters: the function fn to be run on each item and (optional) The scope object for running the function-the value that affects 'foo.

The function (fn) passed in these methods will receive three parameters: item, index, and array. For example:

array.forEach(function(item,index,array){  //do your staff here;},this)

The returned value after the function is executed may/will not affect the returned value in the method.

The functions and return values of these five iteration methods are as follows:

ECMAScript5 Array element Iteration Method

Method Name	Functions	Return Value
Every ()	Run the specified function for each element in the array.	Boolean: returns true if each item is true;
Filter ()	Run the specified function for each element in the array,	Array: a new Array composed of elements returned by function execution and true
ForEach ()	Run the specified function for each element in the array.	Null: No Return Value
Map ()	Run the specified function for each element in the array.	Array: returns a new Array composed of new elements after the function is run.
Some ()	Run the specified function for each element in the array.	Boolean: returns true if any function is executed.

To put it simply:

The every () and some () methods are suitable for conditional judgment on array elements;

The filter () and map () methods are suitable for filtering and reprocessing arrays with conditions;

The forEach () method does not operate on the array itself, but only applies the array element twice;

The following describes how to use the following methods:

Let's assume that you have obtained the company's salary list for this month. Assume that your salary is 9000. The employee salary array of the company is salaries = [,].

A. I want to know if your salary is the lowest;

B. Do you want to know if anyone has the same salary as you have;

C. I want to know if all users are treated the same way;

D. I want to change everyone's salary to K.

Var a, B, c; var your = 9000; var salaries = [,]; a = slaries. some (function (item, index, array) {return item <9000}); console. log (a); // true; congratulations, you still have a lower salary. B = salaries. filter (function (item, index, array) {return item = your;}) console. log (B); // [9000] Haha, someone is treated as you c = salaries. every (function (item, index, array) {return item = your;}); console. log (c); // false. not everyone is treated as you do. d = salaries. map (function (item, index, array) {return item/1000}); console. log (d); // [8.5, 12, 9.9, 9]

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