Javascript code to determine whether an element is implemented in an array _ javascript skills

This article mainly introduces JavaScript code to determine whether an element is implemented in an array. For more information, see I. JQuery

If JQuery is used, you can use the inArray () function:

Jquery inarray () Functions
Jquery. inarray (value, array)
Determine the position of the first parameter in the array (-1 is returned if no value is found ).

Determine the index of the first parameter in the array (-1 if not found ).
Return Value
Jquery
Parameters
Value (any): used to search for existence in the array
Array (array): the array to be processed.

Usage:

The Code is as follows:

$. InArray (value, array)

Ii. Write Functions by yourself

function contains(arr, obj) {  var i = arr.length;  while (i--) {    if (arr[i] === obj) {      return true;    }  }  return false;}

Usage:

The Code is as follows:

Var arr = new Array (1, 2, 3 );
Contains (arr, 2); // return true
Contains (arr, 4); // return false

3. Add a function to Array

Array.prototype.contains = function (obj) {  var i = this.length;  while (i--) {    if (this[i] === obj) {      return true;    }  }  return false;}

Usage:

The Code is as follows:

[1, 2, 3]. contains (2); // return true
[1, 2, 3]. contains ('2'); // return false

4. Use indexOf

However, the problem is that IndexOf is incompatible in some IE versions. You can use the following method:

if (!Array.indexOf) {  Array.prototype.indexOf = function (obj) {    for (var i = 0; i < this.length; i++) {      if (this[i] == obj) {        return i;      }    }    return -1;  }}

First, determine whether the Array has the indexOf method. If not, extend this method.

Therefore, the code above should be written before the code using the indexOf method:

Var arr = new Array ('1', '2', '3'); if (! Array. indexOf) {Array. prototype. indexOf = function (obj) {for (var I = 0; I <this. length; I ++) {if (this [I] = obj) {return I ;}} return-1 ;}} var index = arr. indexOf ('1'); // value 0 for index