Introduction to methods of deleting 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 aspect on the Internet, but some of it is too old and some of the content is not comprehensive enough, so I will sort it out myself. This article 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

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

Pseudo delete

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

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

Complete deletion

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

• start: starting point index value

• deleteCount: the 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
  
  

arr.splice( arr.indexOf( null ), 1 );

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

splice function - replace elements

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

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

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

Now the current array structure is like this:

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

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

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

You can choose to append elements Any position depends 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"]

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

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

Starting position
• arr .indexOf( 'Linda' ) + 1

  is after the array element Linda

The number parameter of deleted elements is set here to 0. This is the key to appending elements, that is Say not to delete elements
'Bill', 'Blake' This is the last parameter items of the splice method of the built-in object Array. It means 0 or more, according to the deleteCount parameter value Different representations have different meanings. The deleteCount parameter here is 0 and items has two values ​​​​to represent this parameter. The example is to append the element values ​​'Bill', 'Blake'

• 
  

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"]

arr.pop();

The deleted array looks like this:

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

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