This repository is a microbenchmark that measures speed of various iteration approaches in javascript.
We measured the following approaches:
// Option 1: regular forEach
array.forEach(cb);
// Option 2: Plain for loop:
for (let i = 0; i < array.length; ++i) cb(array[i])
// Option 3: for .. of loop:
for (let v of array) cb(v)
// Option 4: over iterator:
let iterator = array[Symbol.iterator]();
for (let v of iterator) cb(v);
// Option 4: yield* operator:
yield *array;The benchmark initializes 10,000 vectors vectors, and then computes a square sum of the x dimension
for(let v of vectors) {
sum += v.x * v.x
}Are inconclusive. Most of the time plain old for (let i = 0; i < array.length; ++i) wins, but quite often for .. of
and array.forEach() take the first place.
Iterators and generators were consistently the slowest.
> node --version
v14.4.0
> node arrayIterators.js
array.forEach(cb) x 3,171 ops/sec ±7.49% (72 runs sampled)
for (let i = 0; i < array.length; ++i) cb(array[i]) x 4,989 ops/sec ±5.30% (85 runs sampled)
for (let item of array) cb(item) x 4,711 ops/sec ±3.82% (82 runs sampled)
iterator x 2,880 ops/sec ±4.22% (76 runs sampled)
yield * x 1,498 ops/sec ±1.45% (86 runs sampled)
Fastest is for (let i = 0; i < array.length; ++i) cb(array[i])
We also performed the same set of tests with a Set object. Obviously, we couldn't do plain old
for loop, but the rest of the approaches are still applicable. Here iterators were consistently
the fastest.
node setIterators.js
set.forEach(cb) x 3,340 ops/sec ±3.35% (84 runs sampled)
for (let item of set) cb(item) x 4,364 ops/sec ±5.84% (77 runs sampled)
iterator x 5,919 ops/sec ±1.90% (85 runs sampled)
yield * x 1,616 ops/sec ±2.47% (87 runs sampled)
Fastest is iterator
Again, iterators were faster with maps than any other iteration method:
node mapIterators.js
map.forEach(cb) x 2,214 ops/sec ±4.71% (68 runs sampled)
for (let item of map) cb(item) x 2,060 ops/sec ±9.39% (62 runs sampled)
iterator x 2,454 ops/sec ±5.68% (62 runs sampled)
yield * x 838 ops/sec ±8.09% (54 runs sampled)
Fastest is iterator
If you want to add other tests - please do so. Pull requests are very much welcomed!
- Array vs Object - what is faster: store array of vectors, or encode vectors into array?
- Set vs Object - what is faster: use object fields or Map/Set collections?
MIT