Linear search algorithm in javascript

An simple algorithm to search an item in a given array.

We will implement a simple linear search algorithm to search an item in a given array in javascript. Everything will be written in ES6.

Example

Input:
[1, 2, 3, 4, 5, 6, 10, 11, 15]
5
12
11

Output:
true
false
true

Implementation

• We will iterate through each item in the given array.
• Then in each iteration we will check if element is present or not in the array.
• If it is present then return true else return false.

 let linearSearch = (arr, item) => {
   let found = false;
   
   //loop through each item in the array
   for(let elements of arr){
      if(elements === item){
         found = true;
         break;
      }
   }

   return found;
 };

Input:
console.log(linearSearch([1, 2, 3, 4, 5, 6, 7, 8], 7));
console.log(linearSearch(['prashant','yadav', 23, 25, 27], 'yadav'));
console.log(linearSearch([true, true, true, true], false));

Output:
true
true
false

Time complexity: O(n).
Space complexity: O(1).

Time and Space complexity

• We are iterating through each item in the given array, so Time complexity is O(n).
• We are using constant space, so Space complexity is O(1).

---

Another solution.

We can also implement linear search algorithm by searching for an item in array with array’s inbuilt indexof function of javascript.

 let linearSearch = (arr, item) => {
   return arr.indexOf(item) !== -1 ? true: false;
 }

Input:
console.log(linearSearch([1, 2, 3, 4, 5, 6, 7, 8], 7));
console.log(linearSearch(['prashant','yadav', 23, 25, 27], 'yadav'));
console.log(linearSearch([true, true, true, true], false));

Output:
true
true
false

Time complexity: O(n).
Space complexity: O(1).

Time and Space complexity

• We are using indexOf method to check if item exists in the given array, so Time complexity is O(n).
• We are using constant space, so Space complexity is O(1).