How to query whether there is a certain attribute value in jquery

The method for jquery to query whether there is an attribute value is: 1. Create an HTML sample file and introduce the jQuery file; 2. Create a p tag and set the attribute to "id="my-paragraph" data-role=" paragraph""; 3. jQuery expands to add the "hasAttr()" method; 4. Use the ".attr()" method to get or set the element attribute value, and ".hasAttr()" checks whether the attribute and attribute value are consistent.

The operating system of this tutorial: Windows 10 system, jQuery3.6.0 version, Dell G3 computer.

In jQuery, you can use the `.attr()` method to get or set the attribute value of an element.

If you want to query whether an element has a specific attribute, you can use the `.hasAttr()` method.

The example is as follows:

//html
Lorem ipsum

If you want to check whether this paragraph element has the `data-role` attribute and whether its value is `paragraph`, the code is as follows:

//javascript
if ($("#my-paragraph").hasAttr("data-role") && $("#my-paragraph").attr("data-role") === "paragraph") {
  // do something if the attribute exists and has the expected value
} else {
  // do something else if the attribute doesn't exist or has a different value
}

Note that the `hasAttr()` method is not a built-in method of jQuery. You need to use the following code to extend jQuery to add this method:

//javascript
$.fn.hasAttr = function(name) {
    return this.attr(name) !== undefined;
};

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