Today I Learned - Rocky Kev

TIL how NOT to loop through arrays

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TAGS: javascript arrays

Iterating an array to build another one

If you are iterating an array to build another array from it, you should use map. I've seen this anti-pattern so many times.

// Don't do this:
const numbers = [1,2,3,4,5];
let doubled = [];
numbers.forEach((n, i) => { doubled[i] = n * 2 });


// Do this:
const numbers = [1,2,3,4,5];
const doubled = numbers.map(n => n * 2);

Summing the array of numbers

You want to sum an array of numbers, you should use the reduce method.

const numbers = [1,2,3,4,5];

// Don't do this
const sum = 0;
numbers.forEach(num => {
  sum += num;
});

// Instead
const sum = numbers.reduce((total, n) => total + n, 0);

Via https://stackoverflow.com/a/3010848/4096078

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