Question 189935 in Javascript Question posted in
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Javascript two Arrays: first counts, second values

I have two Arrays they both have the same size and look like this:

a= [ 1, 2, 3, 2] and b = ['this', 'is', 'my', 'good example'].

Array a[i] defines how often the value of b[i] i want to write to a new Array. For my example the result would be c = ['this', 'is', 'is', 'my', 'my', 'my', 'good example', 'good example'].

I tried around with String.repeat but i dont know how to get it to an Array

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3

Answers


  1. 0

    I think this solution will suit you

    const a = [1, 2, 3, 2];
const b = ['this', 'is', 'my', 'good example'];

const c = a.flatMap((count, i) => Array(count).fill(b[i]));

console.log(c);
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  2. 0

    You could just do a loop inside another loop to achieve that

    const a = [1, 2, 3, 2];
const b = ['this', 'is', 'my', 'good example'];

let array = [];
b.forEach((x, i) => {
  for (let j = 0; j < a[i]; j++) {
    array.push(x);
  }
})

console.log(array)
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  3. 0 
    const a = [1, 2, 3],
      b = ['a','b','c']

console.log(
  b.reduce((acc, item, idx) => acc.concat(Array(a[idx]).fill(item)), [])
)

// or the opposite

console.log(
  a.reduce((acc, item, idx) => acc.concat(Array(item).fill(b[idx])), [])
)

    I agree that flatMap is ideal for this task, as answered by @lvjonok

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