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TIL: Array.from has a second argument

stefanjudis profile image Stefan Judis Originally published at stefanjudis.com on ・1 min read

This post is a rather quick one. I followed a Twitter conversation by Surma from Google and Andrea Giammarchi in which Andrea mentionied that Array.from accepts a second argument. I heard this fact a few times before but always forgot it again. Let's hope I'll remember this fact the next time I want to create and transform an Array out of something.

console.log(Array.from([1, 2, 3], x => x + x));
// [2, 4, 6]

The snippet they discussed showed functionality to call a callback X times.

// call a callback `length` times
Array.from({length}, () => callback())

// or generate a random emoji Array
Array.from(
  {length: 7},
  (v, i) => String.fromCodePoint(
    129300 + Math.floor(Math.random() * 20)
  )
);

// [ '🤡', '🤗', '🤥', '🤛', '🤤', '🤦', '🤔' ]

You can read more about Array.from on MDN.

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Stefan Judis

@stefanjudis

DevRel at Contentful. In love with web performance, new technologies, and accessibility – all the good stuff ✌️.

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wow, thx for the tip :)