> > But it seems the thread fizzled out a couple years ago, and > Array.prototype.contains didn't seem to make its way into ES6. That seems > odd, since we do have String.prototype.contains, and it seemed like it was > desirable for DOM. > > The DOM won't inherit from it directly, shall it? >
Why not? A use case would be to check whether a specific node is within a NodeList. > It's also a standard utility function in several libraries. > > Was it left out on purpose? If so, what was the justification? > > I predict code like this without it: > > ''.contains.call([1, 2, 3], 2); // true > > .indexOf === -1 works today for this use case and will continue to. > I'd be happy to see !~arr.indexOf(el) disappear in favor of a use of > .contains() though. > While .indexOf() just gets you the index of one item, .contains() could even be extended to allow to check whether an array contains several items. E.g. .contains([1, 2, 3], [1, 3]) // true .contains([1, 2, 3], [1, 4]) // false Sebastian
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