JSFiddle - React, Tailwind, and code Playground

by Alexey

JavaScript

let arr = [0, 1, 2, 3, 4, 5, 8, 9, 11, 13, 15, 18, 22, 25, 28, 29, 30];
let arr2 = [];
let arr3 = [];

for (var i = 0; i < arr.length; i++) {
  if (arr[i] - arr[i - 1] === 1 || arr[i] - arr[i + 1] === -1) {
    arr2.push(arr[i]);
  } 
}
   for (var y = 0; y < arr2.length; y++) {
   if((arr2[y]-arr2[y+1]) === 1)
   console.log(arr2[y]);
   }
//console.log(arr2);