LinsonLee

let arr = [10, 20, 30, 50, 235, 3000];
console.log(arr.filter(num => ['1','2','5'].includes(num.toString()[0])));

let arr = [10, 20, 30, 50, 235, 3000];

for (let i = 0; i < arr.length; i++) {
  let num = String(arr[i]);
  let char = num[0];
  if (char == 1 || char == 2 || char == 5) {
    console.log(num);
  }
}