Math.floor should work fine - in general you can make use of the implicit conversions of Javascript operations: Two additional options that may be even faster come to my mind: bitwise-or and unary plus. Bitwise-or converts its input to integer-32, unary plus converts to a number. Depending on what the result should be, the most efficient ways with V8 to ensure that something is always a number (or an integer) would be:
y = x | 0 // y is always int32 y = +x // y is always a number (floating point or int) or as already suggested by Mads: y = Math.floor(x) // y is always an integer (possibly larger than int32-range) --Florian Den 21. feb. 2011 00.57 skrev josephlen...@studiofortress.com < josephlen...@gmail.com>: > I'm currently building a language for writing games that compiles > directly to JavaScript. As a part of this I wrap JS arrays inside my > own Array object, and inside it's 'set' method I run 'parseInt' on the > given key to ensure the index is always an int. > > Due to warnings given by the closure JavaScript optimizer I use, today > I changed 'parseInt( key )' to 'parseInt( key, 10 )' (the optimizer > gives you a warning if you fail to do this). However I found that > after adding the radix I received a major performance drop. I'm using > Chrome 11.0.672.2. > > With some of the array intensive examples (namely this one > http://playmycode.com/play/game/Sandbox/Blobs) the loss in framerate > was almost 60% (from around 35fps on my machine to 15fps)! That's > surprising since it's also doing lots of drawing too (although most > time is spent on the number crunching). Simply removing the redux from > parseInt solved this issue and brought the performance back up. > > In my own primitive benchmarks (running parseInt 1000's of times) I > find similar, but with less of a performance drop. I'm just really > stunned that simply supplying the radix can cause such a big drop in > performance. Could this be solved in the future? > > -- > v8-dev mailing list > v8-dev@googlegroups.com > http://groups.google.com/group/v8-dev > -- v8-dev mailing list v8-dev@googlegroups.com http://groups.google.com/group/v8-dev
