FCC - Title Case A Sentence

titleCase.js

var endArr = [],
    firstCap = [],
    finalStr = [];

function theChopper(arr) {
    for (var i = 0; i < arr.length; i++) {
    firstCap.push(arr[i].charAt(0).toUpperCase());
    endArr.push(arr[i].slice(1));
  }
}

function theJoiner(arr1, arr2) {
    var j = 0;
    for (var i = 0; i < arr1.length; i++) {
       finalStr.push(arr1[i] + arr2[j]);
       j++;
    }
}

function titleCase(str) {
  var strArr = str.toLowerCase().split(" ");
  theChopper(strArr);
  theJoiner(firstCap, endArr);
  return finalStr.join(" ");
}

titleCase("He's his own Granpa");