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 10map: 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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