On Wed, Mar 5, 2014 at 7:04 AM, Sebastian Zartner < [email protected]> wrote:
> 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 > String.prototype.contains already has a second parameter for "position" (similar to String.prototype.indexOf), for consistency an Array.prototype.contains should have the same second "fromIndex" parameter as Array.prototype.indexOf. Rick
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