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Benchmark for Array.from
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| const N = 1_000_000; | |
| function map(a, cb) { | |
| const r = Array(a.length); | |
| for (let i = 0; i < a.length; i++) | |
| r[i] = cb(a[i]); | |
| return r; | |
| } | |
| const cb = v => v ** 2; | |
| const funcs = { | |
| 'Array.map()': x => x.map(cb), | |
| 'map()': x => map(x, cb), | |
| 'Array..fill()': x => Array(N).fill().map((_,i) => cb(x[i])), | |
| 'Array.from()': x => Array.from(x, cb), | |
| 'index: Array.from()': _ => Array.from({length: N}, (_, i) => i), | |
| 'index: Array()..fill()': _ => Array(N).fill().map((_, i) => i), | |
| 'empty: Array()': _ => Array(N), | |
| 'empty: Array.from()': _ => Array.from({length:N}), | |
| 'empty: Array()..fill()': _ => Array(N).fill(), | |
| }; | |
| const data = Array.from({length:N}, _ => Math.random()); | |
| for (const [n,f] of Object.entries(funcs)) { | |
| f(data); // warmup | |
| const start = performance.now(); | |
| f(data); | |
| f(data); | |
| f(data); | |
| const end = performance.now(); | |
| console.log(`${n}: ${end - start}`); | |
| } |
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