v151 · web platform · fonts
Interface-Object Probe
Chrome used to mark FontFaceSet with [LegacyNoInterfaceObject], which hid the interface object: typeof FontFaceSet was "undefined" and you could not name the type even though document.fonts was one. Removing that extended attribute exposes the interface object on the global. This probe evaluates the exact expressions the change affects and reports what your browser returns right now.
| expression | expected (Chrome 151+) | this browser |
|---|
what changed
An interface with [LegacyNoInterfaceObject] exists at runtime — objects can be that type — but the constructor name is never installed on the global object. That makes three things impossible: naming the type in code, checking instanceof against it, and reaching its prototype. Removing the attribute installs the interface object, so all three work:
typeof FontFaceSet // "function" (was "undefined")
document.fonts instanceof FontFaceSet // true (was a TypeError: right-hand not callable)
FontFaceSet.prototype.check // function
Object.getPrototypeOf(document.fonts) === FontFaceSet.prototype // trueFirefox and Safari already exposed FontFaceSet; this aligns Chrome with them and with the CSS Font Loading specification.
see also
- instanceof Guards — why exposing the interface object matters to library code.
- Live Font Loader — exercise the FontFaceSet API whose type is now nameable.