Why Does jQuery's ID Selector Only Work with the First Element When Multiple Elements Share the Same ID?

jQuery ID Selector Behavior with Multiple Identical IDs

When working with jQuery, you may encounter an issue where the ID selector ($("#xyz")) seems to retrieve only the value from the first matching element. This behavior can be confusing and frustrating, especially when you expect it to work for all elements with the same ID.

The HTML Code with Identical IDs

Consider the following HTML code, which incorrectly assigns the same ID ("xyz") to three buttons:

<button></button>

The jQuery Code

You might try the following jQuery code to retrieve the value of the clicked button:

$("#xyz").click(function() {
    var xyz = $(this).val();
    alert(xyz);
});

Why It Works Only for the First Button

In this case, the jQuery code will only work for the first button. The jQuery ID selector is designed to select the first element that matches the specified ID. Since the ID "xyz" is repeated multiple times, it returns only the first one.

HTML Invalidity and the Solution

This behavior highlights the importance of ensuring valid HTML code. According to HTML specifications, each ID value must be unique within a document. Having multiple elements with the same ID is invalid and should be avoided.

To rectify the issue, replace the ID with a class attribute for each button:

<button type="button" class="btn btn-primary xyz" value="1">XYZ1</button>
<button type="button" class="btn btn-primary xyz" value="2">XYZ2</button>
<button type="button" class="btn btn-primary xyz" value="3">XYZ3</button>

Updated jQuery Code

To retrieve the value of the clicked button using the updated HTML code, use the class selector:

$(".xyz").click(function() {
    alert(this.value);
});

Note: In this revised code, it's unnecessary to wrap the "this" keyword with $(), as it is already a native JavaScript object.

The above is the detailed content of Why Does jQuery's ID Selector Only Work with the First Element When Multiple Elements Share the Same ID?. For more information, please follow other related articles on the PHP Chinese website!