코드 :

function uppercase(str)
{
  var array1 = str.split(' ');
  var newarray1 = [];
    
  for(var x = 0; x < array1.length; x++){
      newarray1.push(array1[x].charAt(0).toUpperCase()+array1[x].slice(1));
  }
  return newarray1.join(' ');
}
console.log(uppercase("the quick brown fox"));

결과 :

The Quick Brown Fox