Index of closest element in JavaScript

Suppose we have an array like this −

const arr = [2, 42, 82, 122, 162, 202, 242, 282, 322, 362];

We are required to write a JavaScript function that takes in one such array and a number, say n.

The function should return the index of item from the array which is closest to the number n.

Therefore, let’s write the code for this function −

Example

The code for this will be −

const arr = [2, 42, 82, 122, 162, 202, 242, 282, 322, 362];
const closestIndex = (num, arr) => {
   let curr = arr[0], diff = Math.abs(num - curr);
   let index = 0;
   for (let val = 0; val < arr.length; val++) {
      let newdiff = Math.abs(num - arr[val]);
      if (newdiff < diff) {
         diff = newdiff;
         curr = arr[val];
         index = val;
      };
   };
   return index;
};
console.log(closestIndex(150, arr));

Output

The output in the console will be −

4