Introduction to methods of deleting specific elements from JavaScript arrays-JS Tutorial-php.cn

Introduction to methods of deleting specific elements from JavaScript arrays

巴扎黑

Release： 2017-09-07 10:23:24

Original

1534 people have browsed it

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

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

Copy after login

Pseudo delete

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

arr[ arr.indexOf( &#39;Thomas&#39; ) ] = null;

Copy after login

The deleted array looks like this:

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

Copy after login

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

Complete deletion

What is complete deletion? You may also think of this question literally, it is really deleting the array. The element value of Array will change the length of the array. This requirement can be achieved through the splice method of the built-in array object Array! Speaking of the splice method, we need to talk about its specific parameters:

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

Copy after login

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: 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

The element value left by the above pseudo-deletion is deleted through the splice method. null

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

Copy after login

The deleted array looks like this:

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

Copy after login

Now that it’s said By the way, the splice method will talk about its other functions, such as replacing elements, appending elements, etc.!

splice function - replace elements

Now the array structure is like this:

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

Copy after login

I want to replace the array element James with Tom

arr.splice( arr.indexOf( &#39;James&#39; ), 1, &#39;Tom&#39; );

Copy after login

The replaced array structure looks like this:

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

Copy after login

splice function - replace and append elements

Now the current array structure is like this:

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

Copy after login

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

arr.splice( arr.indexOf( &#39;Tom&#39; ), 1, &#39;Judy&#39;, &#39;Linda&#39;, &#39;Alisa&#39; );

Copy after login

The array after replacement and appending The structure looks like this:

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

Copy after login

splice function - append elements

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"]

Copy after login

For example, if you want to add Bill and Blake between Linda and Alisa

arr.splice( arr.indexOf( &#39;Linda&#39; ) + 1, 0, &#39;Bill&#39;, &#39;Blake&#39; );

Copy after login

The appended array structure looks like this:

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

Copy after login

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

Delete the first element in the array

arr.shift();

Copy after login

The deleted array looks like this:

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

Copy after login

Delete the last element in the array

arr.pop();

Copy after login

The deleted array looks like this:

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

Copy after login

The above is the detailed content of Introduction to methods of deleting specific elements from JavaScript arrays. For more information, please follow other related articles on the PHP Chinese website!