Hey, I have another question. I noticed that jquery, underscore and some other libraries, don't check if the index is in array. Under what circumstances this lacking of check will cause a bug? Thank you.
在 2013年5月23日星期四UTC+8下午4时51分21秒，Jakob Kummerow写道： > > Here's what the builtin forEach function does: > https://code.google.com/p/v8/source/browse/branches/bleeding_edge/src/array.js#1078 > > Notably, for every index it checks if the array actually contains that > index. This check is mandated by the ECMAScript specification, see > http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf > chapter 15.4.4.18. > > On Thu, May 23, 2013 at 10:37 AM, 刘玉龙 <[email protected] <javascript:>>wrote: > >> I found an interesting thing in V8 engine when I was testing >> underscore.js library. >> >> For arrays, the >> >>> for (var i = 0; i < len; i++) >> >> implementation can ran 24700 ops(operations per second), while the native >> function >> >>> Array.prototype.forEach >> >> only got 14200 ops. >> >> Then I tried IE10, in which the `nativeForEach` can reach a number of >> 43500. >> >> I checked the source code of V8 engine, but could not find out why this >> native forEach function is so slow. >> Can anybody explain this? Thank you. >> >> -- >> -- >> v8-users mailing list >> [email protected] <javascript:> >> http://groups.google.com/group/v8-users >> --- >> You received this message because you are subscribed to the Google Groups >> "v8-users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] <javascript:>. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> >> > > -- -- v8-users mailing list [email protected] http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
