Critic my "Title case a sentence" implementation

Critic my "Title case a sentence" implementation
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#1
function titleCase(str) {
     str = str.toLowerCase();
  
     return str.split(" ").map(function(element){
            return element.split('');
     }).map(function(ele){
           ele[0] = ele[0].toUpperCase();
           return ele;
     }).map(function(ele){
          return ele.join('');
     }).join(" ");
}

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

This passed the tests