Syntax error Implementing binary search in JavaScript to return the index if the searched number exist

Implementing binary search in JavaScript to return the index if the searched number exist

We are required to write a JavaScript function that takes in a sorted array of numbers as the first argument and a search number as the second argument.

If the search number exists in the array, we need to return its index in the array, otherwise we need to return -1.

We have to do this making use of the binary search algorithm. The binary search algorithm is basically a divide and conquer algorithm which recursive divides the array into halves until it converses to a singleton element.

The sorting of array is necessary of binary search algorithm in this case, as it makes deciding which part to divide easy for us.

Example

const arr = [-3, -1, 4, 7, 9, 11, 14, 22, 26, 28, 36, 45, 67, 78, 88, 99];
const binarySearch = (arr = [], num) => {
   let l = 0;
   let r = arr.length - 1;
   while(l <= r){
      const mid = Math.floor((l + r) / 2); if(num == arr[mid]){
         return mid;
      }
      else if(num < arr[mid]){
         r = mid - 1;
      }
      else{
         l = mid + 1;
      };
   };
   return -1
};
console.log(binarySearch(arr, 22));
console.log(binarySearch(arr, 56));
console.log(binarySearch(arr, 11));

Output

And the output in the console will be −

7
-1
5
Updated on: 2020-11-21T06:09:41+05:30

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