Annie_split

var s = "some_string_to_change",
    a = s.split("_"), // this gives us 4 strings and removes the underscore
    result = a[0]; // this adds the first string to our result
for(i=1;i<a.length;i++) { // loop through each string
  result+= a[i][0].toUpperCase(); // append the uppercase first letter of the string
  result+= a[i].substring(1); // append the rest of the string
}

console.log(result); // log the result to the console