codewars-method-for-counting-with-normal-class.js

// The same thing as the other one, I just changed the syntax of the first two lines to ES6 Classes, if that makes it clearer

class List {
  countSpecDigits(integersList, digitsList){
    // keep a tally of the digits that I see that I'm supposed to count
    const tallyList = digitsList.map(number => [number, 0]);
    // loop over the list of integers
    for(const integer of integersList) {
      const integerDigitList = String(integer).split("").map(Number);
      for(const digit of integerDigitList) {
        // make our check
        // make sure to ignore NaN
        if( digitsList.includes(digit) ) {
          // go into tally list, find the right array and increment to the tally spot
          const tallyPair = tallyList.find(pair => pair[0] === digit);
          tallyPair[1] += 1;
        }
      }
    }
    return tallyList;
  }
}

codewars-method-for-counting.js

function List(){
  this.countSpecDigits=function(integersList, digitsList){
    // keep a tally of the digits that I see that I'm supposed to count
    const tallyList = digitsList.map(number => [number, 0]);
    // loop over the list of integers
    for(const integer of integersList) {
      const integerDigitList = String(integer).split("").map(Number);
      for(const digit of integerDigitList) {
        // make our check
        // make sure to ignore NaN
        if( digitsList.includes(digit) ) {
          // go into tally list, find the right array and increment to the tally spot
          const tallyPair = tallyList.find(pair => pair[0] === digit);
          tallyPair[1] += 1;
        }
      }
    }
    return tallyList;
  }
}