Loop through array multiple times

user_12526657 0
Viewed 1291

How do I repeat the colors array in order, given an unknown length of items?

const items = [1, 2, ...n]
const colors = ['blue', 'green', 'red']

// return ['blue', 'green', 'red', 'blue', 'green'] where items.length = 5
javascript
6 Answers

const items = [1, 2, 3,4,5,6,7,8]
const colors = ['blue', 'green', 'red']

const result = items.map((_,i) => colors[i%colors.length]);

console.log(result);

user_51366590

You can map over a new array with the length you want and take the modulus of the index by the length of the colors array. You do not seem to need the items array at all.

let len = 5;
const colors = ['blue', 'green', 'red'];
const res = Array(len).fill().map((_,idx)=>colors[idx % colors.length]);
console.log(res);

Array.from can also be used in this case.

let length = 5;
const colors = ['blue', 'green', 'red'];
const res = Array.from({length}, (_,idx)=>colors[idx % colors.length]);
console.log(res);

user_95131840

Create a new array and map the values by using the remainder operator %.

const
    items = [1, 2, 3, 4, 5, 6, 7, 8],
    colors = ['blue', 'green', 'red'],
    result = Array.from(items, (_, i) => colors[i % colors.length]);

console.log(result);

user_14476750

When the target size is large, you may get better performance by doubling the array over and over again:

function stretch(arr, n) {
  while (arr.length < n) arr = arr.concat(arr);
  return arr.slice(0, n);
}

const items = [1, 2, 3, 4, 5];
const colors = ['blue', 'green', 'red'];

console.log(stretch(colors, items.length));

user_54598390

You can take mode for index so you can repeat it.

const items = [1, 2, 3,4,5,6];
const colors = ['blue', 'green', 'red'];

var result=[];
items.forEach(myFunction)

function myFunction(item, index) {
  console.log(colors[(index%colors.length)])
  result.push(colors[(index%colors.length)])
}

user_25762540

Using map()

const  items  = [1, 2, 3, 4, 5, 6, 7, 8],
       colors = ['blue', 'green', 'red'];
output = items.map((_,i) => colors[i % colors.length])
     
console.log(output);

user_116067280
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