Let's have a look at the below code snippet and see what's going on

const printToConsole = (function IIFE() {
  let count = 0;
  return function track() {
    if (count <= 0) {
      console.log("Hello World");
      count++;
    } else {
      console.log("Goodbye World");
    }
  };
})();

printToConsole(); // "Hello World"

printToConsole(); // "Goodbye World"

• We define a function printToConsole which has an IFFE (Immediately invoked function definition) assigned to it.
• Inside the IFFE we have our private variable count which we set to 0.
• Then we return a track function which prints the console logs.

The printToConsole function evaluates to this 'track' function which has closure over the count variable.

Closure is the ability to remember the state of a function even when the function (printToConsole) is done running. Without closure the count variable would have been gone and we would get an error.