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util: faster arrayToHash #3964

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util: faster arrayToHash #3964

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3 changes: 3 additions & 0 deletions Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -493,6 +493,9 @@ bench-url: all
bench-events: all
@$(NODE) benchmark/common.js events

bench-util: all
@$(NODE) benchmark/common.js util

bench-all: bench bench-misc bench-array bench-buffer bench-url bench-events

bench: bench-net bench-http bench-fs bench-tls
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15 changes: 15 additions & 0 deletions benchmark/util/inspect.js
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@@ -0,0 +1,15 @@
var util = require('util');

var common = require('../common.js');

var bench = common.createBenchmark(main, {n: [5e6]});

function main(conf) {
var n = conf.n | 0;

bench.start();
for (var i = 0; i < n; i += 1) {
var r = util.inspect({a: 'a', b: 'b', c: 'c', d: 'd'});
}
bench.end(n);
}
5 changes: 3 additions & 2 deletions lib/util.js
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Expand Up @@ -161,9 +161,10 @@ function stylizeNoColor(str, styleType) {
function arrayToHash(array) {
var hash = Object.create(null);

array.forEach(function(val) {
for (var i = 0; i < array.length; i++) {
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I think that avoiding accessing the length property each time will speed up it a little more.

var l = array.length;
var val;
var i;

for (i = 0;  i < l; i++) {
  val = array[i];
  hash[val] = true;
}

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V8 can speedup it with OSR.

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Why make it do more work?

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using let here might have a more clear scope definition?

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v8 is smart enough these days to cache the length automatically, so this shouldn't be an issue.

var val = array[i];
hash[val] = true;
});
}

return hash;
}
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