Summarize and organize the push(), pop(), unshift(), and shift() methods in JavaScript

This article brings you relevant knowledge about javascript, which mainly introduces the use of JavaScript’s push(), pop(), unshift(), and shift() methods, as follows Let's take a look, I hope it will be helpful to everyone.

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Summary introduction:

pop(): This method is used to delete the last element of the array and return the deleted element.

Official syntax:

arrayObject.pop()

shift(): This method is used to delete the first element of the array and return the deleted element.

Official syntax:

arrayObject.shift()

push(): This method is used to add one or more elements to the end of the array and return the new length.

Official syntax:

arrayObject.push(newelement1,newelement2,....,newelementX)

unshift(): This method is used to add one or more elements to the beginning of the array and return the new length.

Official syntax:

arrayObject.unshift(newelement1,newelement2,....,newelementX)

1. push() method

push() method can add one or more elements to the end of the array, and returns the new length.

Syntax:

arrayObject.push(newelement1,newelement2,....,newelementX)

Parameter description:

newelement1: Required. The first element to be added to the array.

newelement2: Optional. The second element to be added to the array.

newelementX: Optional. Multiple elements can be added.

Return value:

The new length after adding the specified value to the array.

Instance:

<script type="text/javascript">

    var arr = new Array(3)
    arr[0] = "George"
    arr[1] = "John"
    arr[2] = "Thomas"

    document.write(arr + "<br />")
    document.write(arr.push("James") + "<br />")
    document.write(arr)

</script>

Output:

##2. pop() method

The pop() method removes and returns the last element of an array.

Syntax:

arrayObject.pop()

Return value:

The last element of arrayObject.

Example:

<script type="text/javascript">

    var arr = new Array(3)
    arr[0] = "George"
    arr[1] = "John"
    arr[2] = "Thomas"

    document.write(arr)
    document.write("<br />")
    document.write(arr.pop())
    document.write("<br />")
    document.write(arr)

</script>

Output:

##3, unshift()

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

Syntax:

arrayObject.unshift(newelement1,newelement2,....,newelementX)

Parameter description:

newelement1: Required. The first element added to the array.
newelement2: Optional. The second element added to the array.
newelementX: Optional. Several elements can be added.
Return value:

The new length of arrayObject.

Example:

<script type="text/javascript">

    var arr = new Array()
    arr[0] = "George"
    arr[1] = "John"
    arr[2] = "Thomas"

    document.write(arr + "<br />")
    document.write(arr.unshift("William") + "<br />")
    document.write(arr)

</script>

Output:

##4, shift()

shift The () method is used to remove the first element from the array and return the value of the first element.

Syntax:

arrayObject.shift()

Return value:

The value of the original first element of the array.

Instance:

<script type="text/javascript">

    var arr = new Array(3)
    arr[0] = "George"
    arr[1] = "John"
    arr[2] = "Thomas"

    document.write(arr + "<br />")
    document.write(arr.shift() + "<br />")
    document.write(arr)

</script>

Output:

[Related recommendations: javascript video tutorial

,

web front end】

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