Run results for: Repeating String

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:50.0) Gecko/20100101 Firefox/50.0

Browser: Firefox 50

Operating system: Mac OS X 10.12

Device Platform: Other

Date tested: 7 years ago

Test name	Executions per second
Simple for loop	6040.2 Ops/sec
Extended for loop	11658.2 Ops/sec
Log based	127897.6 Ops/sec
Array approach	1041.9 Ops/sec

Tests:

Simple for loop
function repeatify(string, repetitions) { if (repetitions < 0 || repetitions === Infinity) { throw new RangeError('Invalid repetitions number'); } let result = ''; for (let i = 0; i < repetitions; i++) { result += string; } return result; } repeatify('*', 10000);
Extended for loop
function repeatify2(string, repetitions) { if (repetitions < 0 || repetitions === Infinity) { throw new RangeError('Invalid repetitions number'); } const isEven = repetitions % 2 === 0; const iterations = Math.floor(repetitions / 2); const stringTwice = string + string; let result = ''; for (let i = 0; i < iterations; i++) { result += stringTwice; } if (!isEven) { result += string; } return result; } repeatify2('*', 10000);
Log based
function repeatify3(string, repetitions) { if (repetitions < 0 || repetitions === Infinity) { throw new RangeError('Invalid repetitions number'); } const cache = new Map(); function repeat(string, repetitions) { if (repetitions === 0) { return ''; } const log = Math.floor(Math.log2(repetitions)); let result; if (cache.has(log)) { result = cache.get(log); } else { result = string; for (let i = 1; i <= log; i++) { result += result; cache.set(i, result); } } const repetitionsProcessed = Math.pow(2, log); const repetitionsLeft = repetitions - repetitionsProcessed; return result + repeat(string, repetitionsLeft); } return repeat(string, repetitions); } repeatify3('*', 10000);
Array approach
function repeatify4(string, repetitions) { if (repetitions < 0 || repetitions === Infinity) { throw new RangeError('Invalid repetitions number'); } return Array(repetitions + 1).join(string); } repeatify4('*', 10000);

Run results for: Repeating String

Simple for loop

Extended for loop

Log based

Array approach