JavaScript/Search/linearSearch.js

/*
 * Linear search or sequential search is a method for finding a target
 * value within a list. It sequentially checks each element of the list
 * for the target value until a match is found or until all the elements
 * have been searched.
 */
function SearchArray (searchNum, ar) {
  var position = Search(ar, searchNum)
  if (position !== -1) {
    console.log('The element was found at ' + (position + 1))
  } else {
    console.log('The element not found')
  }
}

// Search “theArray” for the specified “key” value
function Search (theArray, key) {
  for (var n = 0; n < theArray.length; n++) {
    if (theArray[n] === key) { return n }
  }
  return -1
}

var ar = [1, 2, 3, 4, 5, 6, 7, 8, 9]
SearchArray(3, ar)
SearchArray(4, ar)
SearchArray(11, ar)