Frequency of Elements in One Array that Appear in Another Array Using JavaScript

Problem

We are required to write a JavaScript function that takes in two arrays of strings. Our function should return the number of times each string of the second array appears in the first array.

Example

Following is the code −

 Live Demo

const arr1 = ['abc', 'abc', 'xyz', 'cde', 'uvw'];
const arr2 = ['abc', 'cde', 'uap'];
const findFrequency = (arr1 = [], arr2 = []) => {
   const res = [];
   let count = 0;
   for (let i = 0; i < arr2.length; i++){
      for (let j = 0; j < arr1.length; j++){
         if (arr2[i] === arr1 [j]){
            count++;
         }
      }
      res.push(count);
      count = 0;
   }
   return res;
};
console.log(findFrequency(arr1, arr2));

Output

[2, 1, 0]