- Please enable JavaScript to see the feature test results.
What is it
Feature.js is a fast, simple and lightweight browser feature detection library. It has no dependencies and weighs only 1kb minified and gzipped. Feature.js automatically initializes itself on page load, so you don’t have to. It doesn’t, however, run any tests while initializing, so it will only ever run them when you ask it to. This makes it perform very fast.
With Feature.js, it’s simple to build progressively enhanced experiences that use feature detection to determine if a code can be executed in the user’s browser.
How to use
First, include the script somewhere on your page — usually either in the <head> or just before the </body> closing tag. No need to initialize or do anything else really, all the feature tests are now available for usage:
if (feature.webGL) {
console.log("WebGL supported");
} else {
console.log("WebGL not supported");
}If you want to add a class to the <html> element like Modernizr does when something is supported, that’s simple:
if (feature.webGL) {
document.documentElement.className += " webgl";
}Feature.js also provides an easy way to run all the tests at once and automatically add these classes:
feature.testAll();Combining multiple feature tests is possible too, you can just write an if statement like:
if (feature.canvas && feature.webGL) {
console.log("Canvas and WebGL are supported")
}When you want to target JavaScript only towards browsers that support the features you need, you can check inside a function if the tests return false and stop further execution:
(function() {
if (!feature.webGL || !feature.svg) {
throw new Error("WebGL or SVG isn’t supported");
}
console.log("Browser supports both WebGL & SVG");
})();Gotchas
There are few gotchas related to browser feature detection in general and these things are good to keep in mind when using the Feature.js library.
Touch: Feature.js tries to detect if touch events are supported, but this doesn’t necessarily reflect a touchscreen device. Sometimes you might get a false positive on a device that doesn’t really have touchscreen since it’s virtually impossible nowadays to detect this accurately. For 95-98% of the time this test should be correct though, but you should always keep this in mind when using this detection.
CSS 3D Transforms: Current implementation might give false positive on some older Android stock WebKits in very rare cases. This issue is currently being tracked and will be addressed in the future releases if needed.
Device Motion/Orientation: Keep in mind that many desktop browsers support these event listeners, and will hence give a positive result even though the device might not have the needed sensors.
Placeholders: Feature.js gives false negative for iOS 3 Safari, but since this OS has basically no users, it’s not considered an issue at the moment.
API reference
Below you’ll find a list of all the available feature tests and how to call them. Feature.js has also one public method, testAll, that runs all the tests and adds the supported ones as classes to the <html> element.
feature.async
feature.addEventListener
feature.canvas
feature.classList
feature.cors
feature.contextMenu
feature.css3Dtransform
feature.cssTransform
feature.cssTransition
feature.defer
feature.deviceMotion
feature.deviceOrientation
feature.fetch
feature.geolocation
feature.historyAPI
feature.placeholder
feature.localStorage
feature.matchMedia
feature.pictureElement
feature.querySelectorAll
feature.remUnit
feature.serviceWorker
feature.sizes
feature.srcset
feature.svg
feature.touch
feature.viewportUnit
feature.webGLfeature.testAll();Extending
Feature.js allows you to extend the library with your own tests or customize the existing tests by using the provided extend method:
feature.extend(NAME, CALLBACK);This way you can add your own tests to the library, the result of which will also be integrated with the testAll() method. A simplified example looks like this:
feature.extend("foo", function() {
return true;
});
feature.testAll();The above example would add the foo class to the html element as well.
Utilities
feature.extend graciously exposes the utility methods to your callback. These utilities are used internally within the library and will help unify your added tests:
feature.extend("foo", function(util) {
// Simple create element method
util.create("image"); // returns HTMLElement
// Test if it’s an old device we want to filter out
util.old; // returns Boolean
// Takes standard CSS property as a parameter and returns
// its prefixed version valid for the current browser
util.pfx("transition"); // returns Boolean
});