Immediate Invocation

You can immediately invoke a function after defining it using the not-at-all-hard-to-pronounce acronym "IIFE" (Immediately Invoked Function Expression).

(function () {
  console.log("JavaScript: at least it's not Java");
})();
// JavaScript: at least it's not Java

They can also return values and take arguments:

const result = (function (a, b) {
  return a + b;
})(1, 2);

console.log(result);
// 3

The function is defined and then immediately called. It looks nasty, but it's occasionally useful for a couple of reasons:

• Scope: It has its own scope
• Expression: Can be convenient for computing a value as a single expression (like above)
• Async: Can be used to quickly run code in an async function (we'll cover this later)