03. Anonymous Functions

Conventional functions come with a name linked to its procedure. Anonymous functions, however, don't have a name.

Furthermore, the function is not processed until the statement which it is attached to is declared.

var area = function(width, height) {
  return width * height;
};  // Anonymous function
 
var size = area(3, 4);

Anonymous Functions as Closures

A closure is a function that is passed into another function as an argument.

setTimeout(function() {
  alert("Hello world!");
}, 1000);

The setTimeout function will wait 1000 ms, then send an alert out to the user, displaying "Hello world!" This is an example of an anonymous funciton that is passed into a method as a closure.

Immediately invoked function expressions (IIFE)

Immediately Invoked Function Expressions (IIFE) pronounced iffy are executed once as the interpreter comes across them. These functions are used for a block of code that needs to be run only once.

var area = (function(n) {
  return (n < 1) ? 1 : factorial(n-1) * n;
}(5));

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