A, JQuery

If you are using JQuery, you can use the inArray() function:

Jquery inarray() function

Jquery.inarray (value,array) determines the position of the first argument in the array(-1 if none is found). determine the index of the first parameter in the array (-1 if not found). Returned value jquery parameter value (any) : used to search for array (array) : array to be processed.Copy the code

Usage:

$.inArray(value, array)
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Write your own function

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

var arr = new Array(1.2.3);
contains(arr, 2);/ / return true
contains(arr, 4);/ / returns false
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Add a function to Array

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

[1.2.3].contains(2); / / return true
[1.2.3].contains('2'); / / returns false
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The problem with indexOf, however, is that indexOf is not compatible with some versions of IE. 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) {
                returni; }}return -1; }}Copy the code

Check whether an Array has an indexOf method. If not, extend the method. So the above code should precede the code using indexOf:

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) {
                returni; }}return -1; }}var index = arr.indexOf('1');// Assign 0 to index
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