Analyze the reasons and solutions for why jQuery's on method cannot trigger Ajax

In recent years, Javascript and jQuery have played an increasingly important role in front-end development work. jQuery’s capabilities are not only reflected in its excellent DOM manipulation functions and CSS selectors, but jQuery also provides many powerful global functions. Functions and event processing functions greatly simplify the front-end development workflow. The on() method undoubtedly brings us a lot of convenience, but there is a special case in the use of this method, that is, it cannot trigger the Ajax request. The root cause and solution of this problem will be introduced in detail below.

Usage of on() method

First, let’s understand how to use on() method. The on() method can accept multiple parameters, the most important of which is the first parameter, which is used to specify the type of event, that is, which event the event processing function needs to be bound to.

For example, in the following example, we use the on() method to bind a click event.

$("button").on("click", function(){
    alert("您点击了按钮");
});

The above code will pop up a prompt box after we click the button, in which the on() method passes the click event as the first parameter.

Of course, the on() method can also bind multiple events at the same time (separated by commas), and pass the event processing function into the second parameter. For example:

$("button").on("mouseenter mouseleave", function(){
    alert("您进入/离开按钮区域");
});

The above code will handle the mouse move-in and move-out events of the button at the same time.

The on() method has many other parameters and usages, which will not be described here. For a more detailed introduction, please refer to the jQuery official documentation.

on() method cannot trigger Ajax request? !

Back to the topic of this article, what we will discuss next is the problem that the on() method cannot trigger Ajax requests. Let's take a look at the following example:

$("button").on("click", function(){
    $.ajax({
        url: "http://www.example.com/api",
        type: "GET",
        success: function(response){
            console.log(response);
        }
    });
});

The above code attempts to obtain an API data through an Ajax request when the button is clicked, and prints the response to the console after the request is successful. However, when we click the button, we find that nothing happens and there is no output to the console.

After some exploration and testing, we came to the conclusion: the on() method cannot trigger Ajax requests!

The on() method cannot bind the load event

So, why does the on() method have this problem? The reason is that the on() method actually implements the Ajax request by binding DOM events, and before passing the response data to the processing function, it must first store the data in the DOM node. However, jQuery cannot correctly trigger the load event on all nodes, which causes the on() method to fail to trigger the Ajax request.

We can confirm this through the following code:

$("img").on("load", function(){
    console.log("图片加载完毕");
});

The above code will listen to the image loading completion event and print a message when the event is triggered. However, when we try to load a dynamically generated image (such as <img src="http://www.example.com/1.png">), we will find this paragraph The code doesn't work, nothing is output to the console.

Solution

So, what method should we use when the on() method cannot trigger an Ajax request? The answer is to use jQuery's global function - $.ajax().

$.ajax() method is a low-level function that can implement various types of Ajax requests by passing parameters to it. For example:

$("button").on("click", function(){
    $.ajax({
        url: "http://www.example.com/api",
        type: "GET",
        success: function(response){
            console.log(response);
        }
    });
});

The above code will directly call the $.ajax() function and obtain API data through the GET method. In addition, the $.ajax() function has many other parameters and usages, which will not be described here. For a more detailed introduction, please refer to the jQuery official documentation.

Summary

The above is a detailed introduction and solution to the problem that jQuery's on() method cannot trigger Ajax requests. I hope it can be helpful to everyone. In actual front-end development, we should choose the appropriate method based on the actual situation, pay attention to using good documentation and search engines, and continuously improve our skills and abilities.

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