How to add elements to an array in js

In the previous article, we learned how to use indexes to access elements in array objects. Please see "How js uses indexes to access elements in array objects". This time we will learn how to add elements to an array. You can refer to it if necessary.

In javascript, there are three ways to add elements to an array. Let us look at the first one first.

Let’s look at a small example first.

var arr = new Array(3); 
arr[0] = "one";
arr[1] = "two";
arr[2] = "three";
var newLength = arr.push('four');
console.log(arr);

The result of this small example is

As you can see, in this example, we added an element "## to the end of the array #four”. At the same time, we used the push method. Let's take a look at this function.

push()The method adds one or more elements to the end of the array and returns the new length.

The syntax format is

数组对象.push(要添加到数组的元素)

push() method can add its parameter sequence to the end of

arrayObject. It directly modifies arrayObject instead of creating a new array.

We have finished introducing this method, let’s take a look at the second method.

var arr = new Array(3); 
arr[0] = "one";
arr[1] = "two";
arr[2] = "three";
var newLength = arr.unshift('four');
console.log(arr);

The result is

You can see that we also successfully added an element to the array, but we added it at the head Element "four". This method is different from the previous one, let’s learn this method.

unshift()The method adds one or more elements to the beginning of the array and returns the new length. Move existing elements sequentially to higher subscripts to make space. The first parameter of the method will become the new element 0 of the array, if there is a second parameter it will become the new element 1, and so on.

Please note that the

unshift() method does not create a new array , but directly modifies the original array.

We have finished introducing this method, let’s look at the third method next.

var arr = new Array(3); 
arr[0] = "one";
arr[1] = "two";
arr[2] = "three";
var newLength = arr.splice(1,0,'four');
console.log(arr);

The result is

#You can see that we have also successfully added an element to the array. It seems that this element can be added at any position. Let’s take a look at this method.

splice()The method adds/removes items to/from the array and returns the deleted item.

Let’s take a look at the grammar. The

arrayObject.splice(规定添加/删除项目的位置,要删除的项目数量,向数组添加的新项目)

splice() method removes zero or more elements starting at

index and replaces those elements with one or more values ​​declared in the parameter list. The deleted element. If an element is deleted from arrayObject, an array containing the deleted element is returned.

splice() method

will directly modify the array.

[Recommended learning:

javascript advanced tutorial]

The above is the detailed content of How to add elements to an array in js. For more information, please follow other related articles on the PHP Chinese website!