[Nope, wasn't deliberate] I tested and both are as fast apparently but doing it the "hard" way seems slow. But maybe that's because I didn't do it properly.
And a function isAt could be useful. But it needs another name :-* http://jsperf.com/endswith On Fri, Sep 23, 2011 at 10:22 PM, Axel Rauschmayer <a...@rauschma.de> wrote: > [Was not-cc-ing es-discuss deliberate? Feel free to forward this email if it > wasn’t.] > > Creating a substring isn’t very efficient, either. But I get your point: Why > search the whole string, when it is enough to check a single position? > > A better solution might be to create a helper method > String.prototype.isAt(substr, pos) > that returns true if substr is found at position pos in "this". > > This helper method could be used to implement endsWith and startsWith. > > However, I doubt that the goal for the code was efficiency. > > On Sep 23, 2011, at 22:12 , Xavier MONTILLET wrote: > >> Why doesn't it simply do >> >> String.prototype.endsWith = function(s) { >> return this.substring( this.length - s.length ) === String(s); >> }; >> >> ? >> >> I mean lastIndexOf must be much slower... >> >> On Fri, Sep 23, 2011 at 9:18 PM, Axel Rauschmayer <a...@rauschma.de> wrote: >>> http://wiki.ecmascript.org/doku.php?id=harmony:string_extras >>> I’ve found a small bug: >>> >>> String.prototype.endsWith = function(s) { >>> >>> var t = String(s); >>> return this.lastIndexOf(t) === this.length - t.length; >>> }; >>> >>> Interaction: >>> >>>> "".endsWith("/") >>> true >>>> "#".endsWith("//") >>> true >>>> "##".endsWith("///") >>> true >>> >>> Fix (e.g.): >>> >>> String.prototype.endsWith = function(s) { >>> var t = String(s); >>> >>> var index = this.lastIndexOf(t) >>> return index >= 0 && index === this.length - t.length; >>> }; >>> >>> -- >>> Dr. Axel Rauschmayer >>> a...@rauschma.de >>> twitter.com/rauschma >>> home: rauschma.de >>> blog: 2ality.com >>> >>> >>> >>> _______________________________________________ >>> es-discuss mailing list >>> es-discuss@mozilla.org >>> https://mail.mozilla.org/listinfo/es-discuss >>> >>> >> > > -- > Dr. Axel Rauschmayer > > a...@rauschma.de > twitter.com/rauschma > > home: rauschma.de > blog: 2ality.com > > > > _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
