jquery set data attr

attr() And you can not have to change the data() method.

Try the following way:

console.log($("#you").data("you")); // Hello mean

$("#you").data("you", "yes change you atribute"); // yes change you atribute

console.log($("#you").data("you")); //  yes change you atribute

examples of data http://api.jquery.com/data/​​​​​​

There has already been an answer chosen as a correct one, however its seems like none of the answers clearly and concisely explain what is happening.
So let me give this a shot:

$(element).data(key, value) does not change the html5 'data-*' attributes of the element, jQuery internally stores the key-value (in jQuery.cache).
As a result when you call $(element).data(key) you get what is stored internally by jQuery.

To answer your question here:

Since you are looking to change the data-you attribute of your html tag you will instead need to use the attr() method

Thus:

console.log($("#you").attr("data-you")); // Hello mean

$("#you").attr("data-you", "yes change you atribute");

console.log($("#you").attr("data-you")); // The data-you attribute has been changed.