Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The keys() method of CSSFontFeatureValuesMap instances returns a new map iterator object that contains the [key, value] pairs for each declaration in this CSSFontFeatureValuesMap in insertion order.
keys()None.
A new iterable iterator object.
The following example assigns the keys to the swashKeys variable and then logs the first two values. This example is using @swash but also works with other feature value blocks.
@font-feature-values "MonteCarlo" {
@swash {
swishy: 1;
swashy: 2;
}
}// get the rules
const myRule = document.styleSheets[0].cssRules[0];
// get the keys of swash
const swashKeys = myRule.swash.keys();
console.log(swashKeys.next().value); // logs "swishy"
console.log(swashKeys.next().value); // logs "swashy"