jquery's indexof method

jQuery is a popular JavaScript library that provides many convenient methods to handle operations such as DOM, events, and AJAX. In one of the methods, jQuery provides an indexOf() method, which can be used to find the position of the matching element in the parent element. In this article, we will introduce the usage and examples of jQuery indexOf() method in detail.

The jQuery.indexOf() method is a method of the jQuery object, which is used to find the position of an element in its parent element. The following is the basic syntax for using the jQuery.indexOf() method:

$(selector).index(element)

Here, selector is the jQuery selector, and element is the element object that needs to be found. or selector expression. If the element parameter is not specified, returns the position of the first matching element in its parent element, otherwise returns the position of the specified element in its parent element. Please note that the index values ​​start from 0.

Let's look at some examples of the jQuery.indexOf() method:

Example 1:

In the following example, we find matches in an unsorted list The position of the element.

HTML code:

• apple


• banana


• orange

JavaScript code:

var index = $('li').index($('li:contains("banana" )'));
console.log(index);

Output result: 1
// The position of the 'banana' element in the list is 1 (counting from 0)

Example 2:

In the following example, we will find the position of the first matching element within the parent element.

HTML code:

foo
bar
baz

JavaScript code:

var index = $('.parent').index($(' .parent > span:first'));
console.log(index);

Output result: 0
// The position of the first span element in the parent element is 0 (Counting starts from 0)

Example 3:

In the following example, we will find the position of the second matching element within the parent element.

HTML code:

foo
bar
baz

JavaScript code:

var index = $('.parent').index($(' .parent > span:eq(1)'));
console.log(index);

Output result: 1
// The second span element in the parent element The position is 1 (counting starts from 0)

Example 4:

The jQuery.indexOf() method can also be used to find the position of an element in a jQuery object.

HTML code:

• apple


• banana


• orange

JavaScript code:

var $list = $('li');
var index = $list.index( $list.filter(':contains("banana")'));
console.log(index);

Output result: 1
// The 'banana' element is in the jQuery object The position is 1 (counting from 0)

Summary:

jQuery.indexOf() method is a very practical method in the jQuery library, which can easily find an element in the parent Position within an element or jQuery object. Through the examples provided in this article, we can see the simplicity and convenience of using the indexOf() method. Try this method on your next jQuery project, it will save you a lot of time and effort.

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