const simpleSearch = (list, item) => {
  for (let i = 0; i <= list.length; i++) {
    const candidate = list[i];
    if (candidate === item) {
      console.log(`Item ${item} found at index ${i}`);
      return i;
    }
  }

  console.log(`Not found "${item}"`);
  return null;
};


const list = [10, 20, 30, 50, 80, 100, 500];

simpleSearch(list, 20); // 1
simpleSearch(list, 40); // null