Capitalise the first letter of each word in a string (and otherwise convert to lower case) (JavaScript)

capitaliseFirstWord.js

function titleCase(str) {
  
  var splitString = str.split(" ");
  var newArray = [];
  
  for (var i = 0; i < splitString.length; i++) {
    var splitWord = splitString[i].split("");
    splitWord[0] = splitWord[0].toUpperCase();
    
     for (var j = 1; j < splitWord.length; j++) {
      splitWord[j] = splitWord[j].toLowerCase();
     }
    
    splitWord = splitWord.join(""); 
    newArray.push(splitWord);
  }
  
  return newArray.join(" ");
  
}

titleCase("I'm a LITTLE tea pot");