"Turn" talking about the foreach and each in JavaScript

foreach is a method of manipulating an array in ES5, and the main function is to iterate through the array, for example:

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

Equivalent to:

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

The function callback in the Foreach method has three parameters: the first argument is the array contents of the traversal, the second parameter is the corresponding array index, and the third parameter is the array itself

So:

1 [].foreach (function(value,index,array) {2  3//  Code something4  5 }); 　　　　

Equivalent to:

1 $.each ([],function(index,value,array) {2  3//  code something4  5 }) 　　　

Write an example;

1 var arr = [1,2,3,4]; 2 Arr.foreach (function(value,index,array) {3     array[index] = = value;    // result is true 4     sum+=value;   5     }); 6 console.log (sum);    // The result is ten

Map:map is a "map" that uses the same meaning as a forEach, using the following:

1 [].map (function(value,index,array) {2  3//code  4  5 }) 　　

Reference Documentation:

Https://www.cnblogs.com/fangshidaima/p/5910604.html

"Turn" talking about the foreach and each in JavaScript