src/language-js/print/member.js/printMemberLookup
function printMemberLookup(path, options, print) {
  const property = print("property");
  const node = path.getValue();
  const optional = printOptionalToken(path);

  if (!node.computed) {
    return [optional, ".", property];
  }

  if (!node.property || isNumericLiteral(node.property)) {
    return [optional, "[", property, "]"];
  }

  return group([optional, "[", indent([softline, property]), softline, "]"]);
}