Actual measurement of how jquery data() stores values_jquery

Today I saw a sentence in Chapter 19 of the JS Definitive Guide, saying that jQuery’s data framework does not store element data as element attributes, but it does need to add a special attribute to the element to associate with the data. But what exactly is jQuery? What kind of special attribute has been added? I haven't researched it yet, but I remember that you can get the value of the data-xxx attribute on the HTML tag through jQuery's data("xxx") method.

The test and results are as follows:

Copy the code The code is as follows:

var $demo1 = $("#demo1");
$demo1.data("x",123);
console.log($demo1.attr("x")); //undefined
$demo1 .attr("data-y","abc");
console.log($demo1.data("y")); //"abc"