Where is the default size of a div element defined or calculated?

I wonder how a browser calculates the initial height and width values for div elements without a given size. Given this div for example:

<div>
  TEST
</div>

My browser (Chrome) calculates the size of this div to 1255 x 18, with a windowsize of 1271 x 284. It seems like divs default to the height of a line and the inner width of the window minus some. But I would like to know more about it.

I couldn't find anything here: https://html.spec.whatwg.org/multipage/semantics.html#the-div-element

Where can I find this kind of information?

回答1

div tags are block level elements. All block level elements inherit the width of their parent element by default.

In your example, the div is inheriting the width of the parent body tag, taking into account any margin or padding on the body element.

MDN is usually a great source of information for this sort of thing - see https://developer.mozilla.org/en/docs/Web/HTML/Block-level_elements

回答2

It has display: block so width is 100%, height is auto so it's the size of whatever's inside.