smallest substring of N that contains all the characters in K

smallest_substr.js

// We have an array of strings stored in strArr, which will contain only two strings, 
// the first parameter being the string N and the second parameter being a string K of some characters.
// Your goal is to determine the smallest substring of N that contains all the characters in K.
// For example: if strArr is ["aabdccdbcacd", "aad"] then the smallest substring of N that contains
// all of the characters in K is "aabd" which is located at the beginning of the string.
// Both parameters will be strings ranging in length from 1 to 50 characters and 
// all of K's characters will exist somewhere in the string N. Both strings will only 
// contain lowercase alphabetic characters.

// Examples
// Input: ["ahffaksfajeeubsne", "jefaa"] Output: aksfaje
// Input: ["aaffhkksemckelloe", "fhea"] Output: affhkkse

const input1 = ["aabdccdbcacd", "aaad"]; // "aabdccdbca"
const input2 = ["aabdccdbcacd", "aad"]; // "aabd"
const input3 = ["aaffhkksemckelloe", "fhea"] // "affhkkse"
const input4 = ["ahffaksfajeeubsne", "jefaa"] // "aksfaje"


const subIncludesAll = (str1, str2) => {
   for (let i = 0; i < str1.length; i++) {
      if (str2.indexOf(str1[i]) !== -1) {
         str2 = str2.replace(str1[i], '');
      };
   };
   return (str2.length === 0);
};

const smallestSubString = (input) => {
    const str1 = input[0];
    const str2 = input[1];

   let shortStr = null;
   for (let i = 0; i < str1.length; i++) {
      for (let j = i; j < str1.length; j++) {
         let testStr = str1.substr(i, j-i+1);
         if (subIncludesAll(testStr, str2)) {
            if (shortStr === null || testStr.length < shortStr.length) {
               shortStr = testStr;
            }
         }
      }
   }
   return shortStr;
};

console.log('----------')
console.log('Output: ', smallestSubString(input4))
console.log('----------')