问题
Just a quick question to clear up some confusion that I have regarding units on CSS perspective.
On the CSS Transforms spec it references it with px e.g. perspective: 1000px; but I have used and in many other places others have used it without px e.g. perspective: 1000; such as on W3Schools.
Is either way more preferred? Does it matter?
Just want to clear this up, thanks.
回答1:
Just because it's accepted by (some) browsers doesn't mean it's correct. Specifying a unit of measurement is required by the CSS spec, unless the value is zero.
The spec says:
Lengths refer to distance measurements and are denoted by <length> in the property definitions. A length is a dimension. A zero length may be represented instead as the <number> ‘0’. (In other words, for zero lengths the unit identifier is optional.)
A dimension is a number immediately followed by a unit identifier.
(emphasis mine)
See the Distance Units and the Other Units for examples.
Also see the MDN discussion of length
回答2:
px (or other absolute unit) is the correct way. Here is documentation (better than w3 schools) :)
https://developer.mozilla.org/en-US/docs/CSS/perspective
来源：https://stackoverflow.com/questions/11997177/using-units-on-css-perspective