Check for Majority Element in Array using JavaScript

Given an array of Numbers, any element of the array will be a majority element if that element appears more than array length's 1/2 times in the array.

For example −

If the length of array is 7,

Then if there's any element in the array that appears for at least 4 number of times, it will be considered a majority. And it’s quite apparent that any particular array can have at most one majority element.

We are required to write a JavaScript function that takes in an array of numbers with repetitive values and returns true if there exists a majority element in the array. If there is no such element in the array, our function should return false.

Example

Following is the code −

const arr = [12, 5, 67, 12, 4, 12, 4, 12, 6, 12, 12];
const isMajority = arr => {
   let maxChar = -Infinity, maxCount = 1;
   // this loop determines the possible candidates for majorityElement
   for(let i = 0; i < arr.length; i++){
      if(maxChar !== arr[i]){
         if(maxCount === 1){
            maxChar = arr[i];
         }else{
            maxCount--;
         };
      }else{
         maxCount++;
      };
   };
   // this loop actually checks for the candidate to be the majority element
   const count = arr.reduce((acc, val) => maxChar===val ? ++acc : acc, 0);
   return count > arr.length / 2;
};
console.log(isMajority(arr));

Output

This will produce the following output in console −

true