The latest version of Firefox has support for CSS Variables, but Chrome, IE and loads of other browsers do not. It should be possible to access a DOM Node or write a little method which returns whether the browser supports this feature, but I haven't been able to find anything which is currently able to do this. What I need is a solution which I can use as condition to run code if the browser does not support the feature, something like:
if (!browserCanUseCssVariables()) {
// Do stuff...
}
We can do this with CSS.supports
. This is the JavaScript implementation of CSS's @supports
rule which is currently available in Firefox, Chrome, Opera and Android Browser (see Can I Use...).
The
CSS.supports()
static methods returns a Boolean value indicating if the browser supports a given CSS feature, or not.
– Mozilla Developer Network
With this, we can simply:
CSS.supports('color', 'var(--fake-var)');
The result of this will be true
if the browser supports CSS variables, and false
if it doesn't.
(You might think that CSS.supports('--fake-var', 0)
would work, but as noted in comments on this answer Safari seems to have a bug there making it fail.)
On Firefox this code snippet will produce a green background, as our CSS.supports
call above returns true
. In browsers which do not support CSS variables the background will be red.
var body = document.getElementsByTagName('body')[0];
if (window.CSS && CSS.supports('color', 'var(--fake-var)')) {
body.style.background = 'green';
} else {
body.style.background = 'red';
}
Note that here I've also added checks to see whether window.CSS
exists - this will prevent errors being thrown in browsers which do not support this JavaScript implementation and treat that as false
as well. (CSS.supports
was introduced at the same time CSS
global was introduced, so there's no need to check for it as well.)
browserCanUseCssVariables()
functionIn your case, we can create the browserCanUseCssVariables()
function by simply performing the same logic. This below snippet will alert either true
or false
depending on the support.
function browserCanUseCssVariables() {
return window.CSS && CSS.supports('color', 'var(--fake-var)');
}
if (browserCanUseCssVariables()) {
alert('Your browser supports CSS Variables!');
} else {
alert('Your browser does not support CSS Variables and/or CSS.supports. :-(');
}