sample Array

sampleArray.js

function sampleArray(arr, num) {
  if (arr.length <= num) {
    return arr;
  } else {
    const every = Math.floor(arr.length / num);
    const sampleIndex = Array(num)
      .fill(0)
      .map((_, i) => i * every);

    // keep last element
    if (sampleIndex[sampleIndex.length - 1] < arr.length - 1) {
      sampleIndex.push(arr.length - 1);
    }

    return sampleIndex.map(i => arr[i]);
  }
}