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MIRROR: javascript for 🐜's, a tiny runtime with big ambitions ant.themackabu.dev
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1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950const ITERATIONS = 1_000_000;const source = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];const mapFn = x => x * 2;
// --- Polyfill ---const ArrayFrom_polyfill = function (src, mapFn, thisArg) { if (src == null) { console.error('TypeError: Cannot convert undefined or null to object'); return []; } if (mapFn !== undefined && typeof mapFn !== 'function') { console.error('TypeError: mapFn is not a function'); return []; } const arr = []; let i = 0; if (src[Symbol.iterator] != null) { for (const v of src) arr.push(mapFn ? mapFn.call(thisArg, v, i++) : v); } else { const len = src.length >>> 0; for (; i < len; i++) arr.push(mapFn ? mapFn.call(thisArg, src[i], i) : src[i]); } return arr;};
// --- Builtin ---function benchBuiltin() { const start = performance.now(); for (let i = 0; i < ITERATIONS; i++) { Array.from(source, mapFn); } return performance.now() - start;}
// --- Polyfill ---function benchPolyfill() { const start = performance.now(); for (let i = 0; i < ITERATIONS; i++) { ArrayFrom_polyfill(source, mapFn); } return performance.now() - start;}
const builtinMs = benchBuiltin();const polyfillMs = benchPolyfill();
console.log(`Array.from (builtin): ${builtinMs.toFixed(2)} ms`);console.log(`Array.from (polyfill): ${polyfillMs.toFixed(2)} ms`);console.log(`Ratio: builtin is ${(polyfillMs / builtinMs).toFixed(2)}x ${polyfillMs > builtinMs ? 'faster' : 'slower'} than polyfill`);