<blink>, sure, but String.prototype.blink is still part of the spec, and unlike the HTML Standard, the ECMAScript specs are much more pseudocode that you largely just copy and turn into actual code as necessary, to the point that, if as an ECMAScript host it’s playing the web browser, I’d be extremely surprised (as in, “wait, what!? This is literally the weirdest technical thing I’ve seen all year, maybe this decade”) if that one method wasn’t there. When you’re implementing specs written like this, you just do it all; you don’t—you never—pick and choose based on “that thing is obsolete and no one uses it anyway”.