Capitalized first letter of each word, the rest are lower case.

bonfire-title-case-a-sentence.js

// Bonfire: Title Case a Sentence
// Author: @joepichardo
// Challenge: http://www.freecodecamp.com/challenges/bonfire-title-case-a-sentence
// Learn to Code at Free Code Camp (www.freecodecamp.com)

function titleCase(str) {
  str = str.toLowerCase();
  //make array for each word
  var stringArray = str.split(" ");
  for(var i = 0; i < stringArray.length; i++){
    //store the first character of each word and make it UpperCase
    var stringUpper = stringArray[i].charAt(0).toUpperCase();
    
    //we added the UpperCase letter first then the other
    //characters are added in the for loop
    for(var j = 1; j <= stringArray[i].length; j ++){
      stringUpper = stringUpper + stringArray[i].charAt(j);
    }
    
    //add corrected string to the array to 
    //join the sentence back together
    stringArray[i] = stringUpper;
  }
  str = stringArray.join(" ");
  
  return str;
}

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