CSS variables (Custom Properties) polyfill for IE11
The most complete "Custom Properties polyfill" for Internet Explorer 11.
Used on about 150'000 Live Websites
The IE11 market share is steadily decreasing. I personally have no need to support IE11 anymore.
That's why I have decided to stop working on this project.
--bar:var(--foo)
var(--color, blue)
<style>
, <link>
-elementsstyle.setProperty('--x','y')
style.getPropertyValue('--x')
getComputedStyle(el).getPropertyValue('--inherited')
CSS.registerProperty({name:'--red', inherit:false, initialValue:'#e33'})
(of course not animatable)<div ie-style="--foo:bar"...
!important
on setters and getters (see limitations)inherit
, initial
, unset
and revert
keyword for variablesYou only want IE11 to load the polyfill, use this snippet in the head of your html file, it just works:
<script>window.MSInputMethodContext && document.documentMode && document.write('<script src="https://cdn.jsdelivr.net/gh/nuxodin/[email protected]/ie11CustomProperties.min.js"><\/script>');</script>
The script makes use of the fact that IE has minimal custom properties support where properties can be defined and read out with the cascade in mind. This is not possible with properties starting with double dashes.
.myEl {-ie-test:'aaa'} // only one dash allowed! "-"
then you can read it in IE with javascript:
getComputedStyle( querySelector('.myEl') )['-ie-test']
In the raw CSS, it replaces for example --foo
with -ie-foo
.
It searches for all rules containing variable getters and setter, remembers the affected selectors so future affected Elements can be found in a mutation observer.
Each affected Element gets a uniq class-attribute and its own style-sheet to draw the Element.
These are the steps that the script does:
header { --myColor:red; }
main { --myColor:green; }
li { color:var(--myColor); }
header { -ie-myColor:red; }
main { -ie-myColor:green; }
li { -ieHasVar-color:var(-ie-myColor); }
querySelectorAll('li').forEach(function(){
var color = getComputedStyle(this).getPropertyValue('--myColor');
// getPropertyValue is extended to handle custom properties
// draw_the_Element()
})
li.iecp-u1 { color:red; }
li.iecp-u2 { color:red; }
li.iecp-u3 { color:green; }
li.iecp-u4 { color:green; }
There is no way to get the raw content of style-attributes in IE11.
Use <div style="--color:blue" ie-style="--color:blue">
for this.
...is always little higher if vars are not served by root, because each selector gets an additional class-selector
eg. #header
results in #header.iecp_u44
vars in @import is not supported at the moment
There are problems with !important. I need a minimal, reproducible testcase on https://jsbin.com/
If you'd prefer the polyfill to ignore (not run) on a particular stylesheet add the iecp-ignore tag to the link element.
See the tests
PRs welcome