js.bench[0] = 'effective "with"?'
(function($){ var bench = function(f){ for(var t = new Date, i = 1024; i--;) f(); return (new Date - t) / 1024; }, c = bench(function(){}), r = [], k; for(k in $){ r.push(k +': '+ (bench($[k]) - c) +" [ms]") } confirm(r.join("\n\n")); })({ /// どっちが速い? /// A: function(){ for(var i = 100; i--;) Math.random() } , B: function(){ with(Math) for(var i = 100; i--;) random() } })