A brief introduction to foreach and each in JS

In the previous article, we introduced the detailed explanation of the foreach statement in JS. I believe that everyone has a certain degree of familiarity and understanding of the use of the foreach statement, so today we will continue to introduce JS to you. Foreach and each

forEach is a method of operating array in ES5. The main function is to traverse the array, for example,

var arr = [1,2,3,4];
arr.forEach(alert);

is equivalent to :

var arr = [1, 2, 3, 4];
for (var k = 0, length = arr.length; k < length; k++) {
 alert(array[k]);
}

The function callback in the forEach method has three parameters: the first parameter is the traversed array content, the second parameter is the corresponding array index, and the third parameter is the array Itself

Therefore:

[].forEach(function(value,index,array){
　　　　//code something
　　});

is equivalent to:

　$.each([],function(index,value,array){
　　　　//code something
　　})

Write an example;

var arr = [1,2,3,4];
arr.forEach(function(value,index,array){
    array[index] == value;    //结果为true
    sum+=value;   
    });
console.log(sum);    //结果为 10

map: map means "mapping". Usage and forEach is similar, the usage is:

[].map(function(value,index,array){
　　//code
})

Summary:

This article introduces in detail the introduction of foreach and each in JS, do you believe it? I have a deep understanding and understanding of this, I hope it will be helpful to your work!

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