Understand the role and application scenarios of eq in jQuery

jQuery is a popular JavaScript library that is widely used to handle DOM operations and event handling in web pages. In jQuery, the eq() method is used to select elements at a specified index position. The specific usage and application scenarios are as follows.

In jQuery, the eq() method selects the element at the specified index position. Index positions start counting from 0, i.e. the index of the first element is 0, the index of the second element is 1, and so on. The syntax of the eq() method is as follows:

$("selector").eq(index);

Among them, $("selector") represents the element to be selected, which can be any valid jQuery selector, indexIndicates the index position of the element to be selected. There are many application scenarios for the

eq() method. For example, it is often used in processing common interactive effects on web pages such as carousels, tabs, and waterfall flows. The following uses specific code examples to demonstrate the usage scenarios of the eq() method.

Example 1: Carousel image

Suppose there is a simple carousel image consisting of several pictures. We want to achieve the effect of clicking to switch pictures. You can Use the eq() method to select the currently displayed image and the next image to be displayed.

<div class="slider">
  <img src="image1.jpg" alt="Image 1">
  <img src="image2.jpg" alt="Image 2">
  <img src="image3.jpg" alt="Image 3">
</div>

<button id="prevBtn">上一张</button>
<button id="nextBtn">下一张</button>

$("#nextBtn").click(function(){
  var currentImgIndex = $(".slider img.active").index();
  var nextImgIndex = (currentImgIndex + 1) % $(".slider img").length;
  
  $(".slider img").removeClass("active").eq(nextImgIndex).addClass("active");
});

$("#prevBtn").click(function(){
  var currentImgIndex = $(".slider img.active").index();
  var prevImgIndex = (currentImgIndex - 1 + $(".slider img").length) % $(".slider img").length;
  
  $(".slider img").removeClass("active").eq(prevImgIndex).addClass("active");
});

In the above code, we use the eq() method to select the currently displayed picture and the next/previous picture to be displayed, and switch pictures by clicking the button.

Example 2: Tab

Another common application scenario is tabs, which display different content when the user clicks on different tabs. We can use the eq() method to select the corresponding content for display.

<div class="tab">
  <ul class="tab-nav">
    <li>标签1</li>
    <li>标签2</li>
    <li>标签3</li>
  </ul>
  <div class="tab-content">
    <div>内容1</div>
    <div>内容2</div>
    <div>内容3</div>
  </div>
</div>

$(".tab-nav li").click(function(){
  var index = $(this).index();
  
  $(this).addClass("active").siblings().removeClass("active");
  $(".tab-content div").removeClass("active").eq(index).addClass("active");
});

In the above code, we use the eq() method to select the corresponding content for display. When the user clicks on a different label, the corresponding content is displayed, achieving the effect of a tab.

In summary, the eq() method is a commonly used method in jQuery, used to select elements at specified index positions. When dealing with various interactive effects, the eq() method can help us accurately select the elements that need to be operated, making web page interaction more flexible and diverse. I hope that through the introduction of this article, readers can have a deeper understanding of the role and application scenarios of the eq() method.

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