Delete specified elements from JS array

This time I will bring you JSarrayDeleteSpecify the element, JS array delete the specified elementWhat are the precautions, the following is a practical case, one Get up and take a look.

In everyone's use of JavaScript, deleting specific elements from arrays has always been a problem for many people. How to delete specific elements from JavaScript arrays? The following article will give you a detailed introduction.

Source array

var arr = ["George", "John", "Thomas", "James", "Adrew", "Martin"];

Pseudo delete>

What is pseudo-deletion? That is to say, setting the array element value to null;

arr[ arr.indexOf( 'Thomas' ) ] = null;

The deleted array looks like this:

["George", "John", null, "James", "Adrew", "Martin"]

However, please note that this means that the length of the array Array, that is, the variable arr, remains unchanged

Completely delete

What is complete deletion? You may also think of this question literally, which is to actually delete the element values ​​​​of the array Array, and will change the length of the array. You can use the splice method of the built-in array

object Array. Fulfill this need! When it comes to the splice method, let’s talk about its specific parameters:

Array.prototype.splice = function(start,deleteCount,items) {};

The above is the prototype definition of the splice method of the built-in object Array. The Chinese meaning is: splicing, and the meaning of its parameters is:

• start: starting point

  index value

deleteCount: number of elements to be deleted
items: elements replaced/appended after deletion When the parameter is not added, it means deleting the element, and it must be combined with the parameter value of deleteCount. If deleteCount is 1, and a parameter value is given in the items parameter position, it means replacement If deleteCount is 1 and more than one parameter value is given in the items parameter position, it means replacing and appending elements

Use the splice method to delete the element value left by the above pseudo-deletion null

arr.splice( arr.indexOf( null ), 1 );

The deleted array looks like this:

["George", "John", "James", "Adrew", "Martin"]

Now that we have mentioned the splice method, let’s talk about its other functions, such as replacing elements, appending elements, etc.!

splice function - replace element

Now the array structure is like this:

["George", "John", "James", "Adrew", "Martin"]

Want to replace array element James with Tom

arr.splice( arr.indexOf( 'James' ), 1, 'Tom' );

The replaced array structure looks like this:

["George", "John", "Tom", "Adrew", "Martin"]

splice function - replaces and appends elements

Now the current array structure is like this:

["George", "John", "Tom", "Adrew", "Martin"]

Want to replace array element Tom with Judy and append Linda and Alisa

arr.splice( arr.indexOf( 'Tom' ), 1, 'Judy', 'Linda', 'Alisa' );

The array structure after replacement and appending looks like this:

["George", "John", "Judy", "Linda", "Alisa", "Adrew", "Martin"]

splice function - append element

You can choose any position to append elements, depending on your specific needs. The key lies in the value index position of start! The current array structure is as follows:

["George", "John", "Judy", "Linda", "Alisa", "Adrew", "Martin"]

For example, add Bill and Blake

arr.splice( arr.indexOf( 'Linda' ) + 1, 0, 'Bill', 'Blake' );

between Linda and Alisa The appended array structure looks like this:

["George", "John", "Judy", "Linda", "Bill", "Blake", "Alisa", "Adrew", "Martin"]

• The starting position

  arr.indexOf( 'Linda' ) 1 is after the array element Linda

The number of deleted elements parameter is set here to 0. This is the key to appending elements. That is to say, the elements are not deleted.
'Bill', 'Blake' This is the last parameter items of the splice method of the built-in object Array. It means 0 and more, according to deleteCount Different parameter values ​​have different meanings. Here the deleteCount parameter is 0 and items has two values ​​to represent this parameter. In this case, the element values ​​'Bill', 'Blake'

• are appended.

The above is about deleting specific elements in the array. It is too simple to delete the first element and the last element. I will briefly mention it here

Delete the first element in the array

arr.shift();

The deleted array looks like this:

["John", "Judy", "Linda", "Bill", "Blake", "Alisa", "Adrew", "Martin"]

Delete the last element in the array

arr.pop();

The deleted array looks like this:

["John", "Judy", "Linda", "Bill", "Blake", "Alisa", "Adrew"]

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

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