How to delete elements in an array in es6

Deletion method: 1. Use shift() to delete the first element, the syntax "arr.shift()"; 2. Use pop() to delete the last element, the syntax "arr.pop()"; 3. Use splice() to delete any element based on the subscript, the syntax is "arr.splice (start subscript, delete the number of elements)".

The operating environment of this tutorial: Windows 7 system, ECMAScript version 6, Dell G3 computer.

In JavaScript, there are many ways to delete array elements. Here are some of them.

Method 1: Use the shift() function to delete the first array element

array.shift() function can delete the first element of the array from it, And return the value of the first element; then move all remaining elements forward by 1 position to fill the gap at the head of the array.

var a = [1,2,3,4,5,6,7,8];  //定义数组
a.shift();
console.log(a);

The output result is:

It can be seen that the above example uses a.shift() to delete the value 1 at the beginning of the a array, and then it will be repeated Set the index (restart from 0); and the shift() method will change the original array and modify the length of the array! Therefore, use console.log(a) to output the original array, which displays the array whose first element has been deleted.

Method 2: Use pop() to delete the last array element

array.pop() method can delete the last element in the array and return the deleted element.

var a = [1,2,3,4,5,6,7,8];  //定义数组
a.pop();
console.log(a)

The output result is:

It can be seen that the above example uses a.pop() to delete the end of the a array The value is 8, and then the index will be reset (starting from 0 again); and the pop() method will also change the original array and modify the length of the array!

Method 3: Use splice() to delete any element based on the array subscript

Use splice() to delete one or more elements starting from the specified subscript position.

Syntax for deleting elements:

array.splice(index,howmany)

• The first parameter index can specify the starting subscript position (that is, the position where the element is deleted) ;

• The second parameter howmany specifies the number of elements that should be deleted (that is, one or more elements that need to be deleted).
  

Let’s take a closer look at the following example:

var arr= [1,2,3,4,5];
console.log(arr);

arr.splice(1,2);
console.log(arr);

It can be seen that: use arr.splice(1,2)Delete 2 elements starting from the position of subscript 1 (the second element of the array), that is, arr[1] and arr[2] are deleted, so the output result is :

Using the splice() method, we can also delete elements at the beginning and end of the array:

• If you want To delete an element at the beginning of the array, just set the value of the first parameter index of the method to 0

var arr= [1,2,3,4,5];
console.log(arr);

arr.splice(0,2);
console.log(arr);

• If If you want to delete elements at the end of the array, set the value of the first parameter index of the method to a negative number, then it will be positioned from the right side of the array to the left according to the absolute value; and the value of the second parameter howmany must be equal to index value.

var arr= [1,2,3,4,5];
console.log(arr);

//从倒数第二个元素开始，截取两个元素
arr.splice(-2,2);
console.log(arr);

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