I dont understand how this for loop is calling itself

function titleCase(str) {
  const newTitle = str.split(" ");
  const updatedTitle = [];
for (let st in newTitle) {
    updatedTitle[st] = newTitle[st]
      .replace(newTitle[st].charAt(0), newTitle[st].charAt(0).toUpperCase());
  return updatedTitle.join(" ");

Can someone explain the syntax in the for loop here? The only syntax I understand is the ([initalize], [condition], [resolution]).

It’s a for in loop, which loops over properties of an object. In addition to that, there’s also a for of loop, which loops over the values in an iterable (usually an array). These both come up somewhere in the fCC curriculum.