So maybe you’ve heard of JavaScript closures before but you’re wondering, what exactly are they? Well, when it comes to JavaScript, you can have variables that belong to a local (a variable declared within a specific function) or global scope (variables that are accessible from anywhere in the code). You can make variables private by using closures.

Take a look at the following example:

var countUp = (function () {
var count = 0;
return function () {return count += 1;}
})();

countUp();

Now, let’s break it down:

• The variable countUp is assigned the value of a self-invoking function.
• It sets the count to 0 and returns a value that adds 1 to the current count.
• It has access to the count in the parent scope.
• The variable count is protected by the scope of the anonymous function, and can only be changed using the countUp function.