Mastering JavaScript Functional Programming - Second Edition

Solution 7 – using a local flag

We can go back to the idea of using a flag, but instead of making it global (which was our main objection), we can use an Immediately Invoked Function Expression (IIFE), which we'll see more on in Chapter 3, Starting Out with Functions – A Core Concept, and Chapter 11, Implementing Design Patterns – The Functional Way. With this, we can use a closure, so clicked will be local to the function, and not visible anywhere else:

var billTheUser = (clicked => {  return (some, sales, data) => {    if (!clicked) {      clicked = true;      window.alert("Billing the user...");      // actually bill the user    }  };})(false);

See how clicked gets its initial false value from the call at the end.

This solution is along the lines of the global ...