linearSearch javascript Code Snippet in 2025

Finds the first index of a given element in an array using the linear search algorithm.

• Use a for...in loop to iterate over the indexes of the given array.
• Check if the element in the corresponding index is equal to item.
• If the element is found, return the index, using the unary + operator to convert it from a string to a number.
• If the element is not found after iterating over the whole array, return -1.

const linearSearch = (arr, item) => {
  for (const i in arr) {
    if (arr[i] === item) return +i;
  }
  return -1;
};

linearSearch([2, 9, 9], 9); // 1
linearSearch([2, 9, 9], 7); // -1