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How to solve jquery selected not changing problem

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Release： 2023-04-17 13:40:48

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When developing websites, we often use jQuery to manipulate DOM elements. One common operation is to select elements and modify their properties or content. In jQuery, you can use selectors to select elements that need to be operated. However, sometimes we find that although elements have been selected through the selector, modifying their attributes or content does not take effect. So, how to solve this situation?

Case Demonstration

Let us look at a simple case to better understand the problem. Below is an HTML file that contains some paragraphs and buttons:

<!DOCTYPE html>
<html>
<head>
    <title>jQuery selected没有改变</title>
</head>
<body>
    <p id="para1">Hello World!</p>
    <p class="para2">jQuery is awesome!</p>
    <button id="btn1">改变段落内容</button>
    <button id="btn2">改变按钮文本</button>

    <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
    <script>
        $(document).ready(function(){
            $("#btn1").click(function(){
                $("#para1").text("Paragraph 1内容已改变！"); //改变段落1的内容
            });

            $("#btn2").click(function(){
                $(".para2").text("Paragraph 2内容已改变！"); //改变所有class为para2的段落的内容
            });
        });
    </script>
</body>
</html>

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As you can see, in this case, we used jQuery to select two elements. One is the paragraph with the ID "para1", and the other is all the paragraphs with the class "para2". We're trying to use jQuery to modify the content of the buttons when they are clicked.

Cannot change content

However, when we run the example and try to change the content of the paragraph to the new value, we find that there is no change.

There are a few possible reasons here:

There is a spelling error in the code that prevents the code from executing as expected.
The selector does not select the actual element.
The code attempts to change a property or property value that cannot be changed.

If this problem occurs, we can use the browser's developer tools to check the cause of the problem.

Debug Code

In this example, open your browser's developer tools (press F12) and select the "Elements" tab in the HTML code. In this tab, you can view the values of DOM elements as well as CSS properties.

We will see that the value in the first paragraph has not been modified correctly, but is still "Hello World!", and the content of the second paragraph has not been modified to "Paragraph 2 content has been changed." Change!". This means we need to check selectors and code.

Check the selector

First, check whether the selector selects the correct element. In this example, we use two selectors: an ID selector and a class selector. Use the # symbol in the selector to represent the ID selector, and use the . symbol to represent the class selector.

For example, the selector "#para1" will select the element with the id "para1"; the selector ".para2" will select all elements with class "para2".

Make sure there are no errors in the selector.

Check the code

Next, check whether the code is correct. In this example, we are trying to modify the content of the paragraph in the handler of the button click event. We use jQuery's .text() method to modify the content of the paragraph.

For example, $("#para1").text("Paragraph 1 content has changed!"); will select the paragraph with the element ID "para1" and change its text to "Paragraph 1 content has been changed!" Change!".

Make sure the code calls the correct methods and properties and has no syntax errors.

solve the problem

By inspecting the selector and code, we can discover the cause and solve the problem.

In this example, when we inspected the code, we found that the modification operation was not performed correctly. The reason is that we did not make the correct call when modifying the operation. We should use the following code:

$(document).ready(function(){
    $("#btn1").click(function(){
        $("#para1").text("Paragraph 1内容已更改！");
    });
 
    $("#btn2").click(function(){
        $(".para2").text("Paragraph 2内容已更改！");
    });
});

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After correctly executing the above code, we reload the web page. Now, we find that it works fine and the content of the paragraph is successfully modified.

Summary

This article briefly introduces the problems that may arise when selecting elements and modifying their properties or content in jQuery. When a problem occurs, we should use the browser's developer tools to check the code and selectors to locate the cause of the problem. Only by checking and modifying the code can the problem be finally solved and the normal operation of the web page ensured.

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