Explain how to use jQuery to handle caching

jQuery is a very popular JavaScript library that is widely used in Web development, and caching is a very important concept in Web development. jQuery also provides some methods to help deal with caching. This article will explain how to use jQuery to handle caching.

1. Ajax cache in jQuery

When using jQuery to make an Ajax request, you will find that the result of the request will be cached, that is, when the request is made again, the result in the cache will be used directly. The request will not be made again. This caching mechanism can improve the performance of Ajax, but sometimes it can also cause problems. For example, when the data changes and the cache is still valid, then we need to use some methods provided by jQuery to control the behavior of the cache.

1. Cache Control

jQuery provides a global cache configuration option, which can be set to control whether to enable caching during Ajax requests. This option defaults to true, which enables caching. You can use the following statement to disable the global cache:

$.ajaxSetup({cache: false});

Of course, you can also set the cache in a single Ajax request:

$.ajax({
  url: "test.html",
  cache: false,
  success: function(result){
    $("#div").html(result);
  }
});

2. Manually clear the cache

If we want to manually clear the cache after requesting the results, we can use the following statement:

$.ajax({
  url: "test.html",
  success: function(result){
    $("#div").html(result);
    $.ajaxSetup({cache: false});
  }
});

This statement will disable the global cache after the request results are loaded.

2. DOM caching in jQuery

In addition to Ajax caching, jQuery also provides a DOM caching mechanism, which caches DOM elements for later use. DOM caching can improve JavaScript performance because DOM operations are relatively slow. Let's take a look at how to do DOM caching in jQuery.

1. Caching DOM objects

Caching DOM objects is very simple, just store the DOM object in a JavaScript variable.

For example, we need to frequently operate on a DOM element:

$("#myDiv").addClass("selected");
$("#myDiv").fadeOut();
$("#myDiv").html("Hello World");

Such code will cause multiple DOM queries and affect performance. We can cache DOM objects, the code is as follows:

var $myDiv = $("#myDiv");
$myDiv.addClass("selected");
$myDiv.fadeOut();
$myDiv.html("Hello World");

Using $myDiv variable instead of $("#myDiv") can greatly reduce DOM queries and improve performance.

2. Caching jQuery objects

If we need to operate on multiple DOM elements, we need to cache a jQuery object. A jQuery object is a collection containing multiple DOM elements, and you can use the methods it provides to operate on the elements in the collection.

For example, we need to operate multiple li elements at the same time:

$("li").addClass("selected");
$("li").fadeOut();
$("li").html("Hello World");

Similarly, such code will cause multiple DOM queries. We can store jQuery objects in a variable.

var $lis = $("li");
$lis.addClass("selected");
$lis.fadeOut();
$lis.html("Hello World");

Using $lis variable instead of $("li") can greatly reduce DOM queries and improve performance.

Summary

This article introduces how jQuery handles caching. In Ajax requests, we can use global cache configuration options or specify cache options in individual requests to control the behavior of the cache. In DOM operations, we can cache DOM objects or jQuery objects to improve JavaScript performance. Of course, caching is not a panacea, and you need to decide whether to use caching based on the actual situation.

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