We are required to compare the time taken respectively by the ES6 functions forEach() and reduce() for summing a huge array of numbers.
As we can't have a huge array of numbers here, we will simulate the magnitude of array by performing the summing operation for large number of times (iterations)
Example
Let's write the code for this −
const arr = [1, 4, 4, 54, 56, 54, 2, 23, 6, 54, 65, 65]; const reduceSum = arr => arr.reduce((acc, val) => acc + val); const forEachSum = arr => { let sum = 0; arr.forEach(el => sum += el); return sum; }; const iterations = 1000000000; console.time('reduce'); for(let i = 0; i < iterations; i++){ let sumReduce = reduceSum(arr); }; console.timeEnd('reduce'); console.time('forEach'); for(let j = 0; j < iterations; j++){ let sumForEach = forEachSum(arr); }; console.timeEnd('forEach');
Output
Following is the output in the console −
reduce: 19.058s forEach: 45.204s
So roughly, the ratio of time taken by Array.prototype.reduce() to the time taken by Array.prototype.forEach is 1 : 1.4