export default.txt

// named function
export default function add(x, y) {
  return x + y;
}

// anonymous function
export default function(x, y) {
  return x + y;
}
Since export default is used to declare a fallback value for a module or file, you can only have one value be a default export in each module or file. Additionally, you cannot use export default with var, let, or const

import add from "./math_functions.js";
(no curly braces around function name, use any name here when importing a default)