Summary of several methods to delete specific elements from JavaScript arrays

Deleting specified elements from js arrays is a problem that each of us encounters. There is a lot of information on this online, but some are too old and some are not comprehensive enough. So I will organize it myself. This article mainly summarizes and introduces various methods for deleting specific elements in JavaScript arrays. Friends in need can refer to it.

Preface

Maybe when it comes to deleting specific elements of an array, you estimate that there is more than one way to achieve it, so let’s take a look. Check out these methods I’ve summarized, they may be helpful to you! Not much to say, let’s take a look at the detailed introduction.

Source array

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

Pseudo deletion

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"]

But please note that this means that arrayArraythat is, the length of variable arr remains unchanged

Delete completely

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. To realize this requirement! Speaking of 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. 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 replacing
  If deleteCount is 1 and the items parameter position is given to more than one parameter value, it means replacing and appending elements
  
  

The element value left by the above pseudo-deletion is deleted through the splice method. 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 me talk about its other functions, such as replacing elements, appending elements, etc. Do it!

spliceFunction - Replace elements

Now the array structure is like this:

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

Want to replace the 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 - replace and append Element

Now the current array structure is like this:

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

I want to replace the 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 is like this:

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

splice function - append elements

Append elements you You can choose any position 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, if you want to add Bill and Blake between Linda and Alisa

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

The added array structure looks like the following ：

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

• 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, which means that the elements are not deleted.

• 'Bill', 'Blake' This is the built-in The last parameter items of the splice method of the object Array represents 0 or more. The meaning will be different depending on the deleteCount parameter value. Here the deleteCount parameter is 0 and items has two values ​​​​to represent this parameter, as shown That is to say, append the element value 'Bill', 'Blake'

  
  

#The above is to delete specific elements in the array, then delete the first element and the last element to achieve It’s too simple now, just mention it here briefly

Delete the first element in the array

arr.shift();

The array after deletion looks like this:

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

Delete the last element in the array

arr.pop();

After deletion The array looks like this:

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

The above is all the content of this article. I hope it can help everyone learn JavaScript! !

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