How does jQuery FadeIn know the used display mode?

Question

Simple question: How does jQuery know what display mode an element should use when using fadeIn?

What I mean, is that it appears to use the proper display mode for any element that I fadeIn, even when I set display:none initially in my CSS - images are using inline, divs are using block, etc.

I looked into the jQuery source code on GitHub, but I couldnt locate what I was looking for.

Reason I ask is because I am making a little plugin myself, using fade (but with Animate, since there is more than 1 property that needs animation).

Answer 1

It uses $.data to store it:

console.log($._data( elem, "olddisplay" ));

The underscore means that it can access data that is not normally available through $.data or $.fn.data. Basically this is for internal use only and you should not touch it.

If the element is set to display:none through CSS, and you fade it in, jQuery still knows to make it inline etc. In this case, it uses the function

// Try to determine the default display value of an element
function css_defaultDisplay( nodeName ) {

Which would give "inline" for a nodeName === "span"