Book: JavaScript

(Note: This was going to be where I was keeping notes to eventually write a book. Needless to say, there’s not much here and the book never happened!)


Parenthesis and function execution

Parenthesis kick off the execution of a function:

function foo() {
	return true;

typeof foo;    // "function"
typeof foo();  // "boolean"

Both of these are related to the function we just defined, but notice that a function reference without parenthesis is simply a pointer to the function and nothing more. The function with parenthesis executes our function and returns a result (true, which is of type “boolean”). We can assign these to variables:

var myFunction = foo;  // store the function pointer
var myResult = foo();  // store the result of executing the function

typeof myFunction;     // "function"
typeof myResult;       // "boolean"

Passing parameters

-passing objects

Self-executing anonymous functions

A self-executing anonymous function is an unnamed function that’s simply executed immediately after being defined. Here’s an example:


Just as above, we can pass in parameters:

	param;  // "foo"

Why on earth would you want to use this? As it turns out, this is a nice way to sandbox your code and is preferred to simply declaring code out in the open. Have a look at the difference:

// Old way (antipattern!)
var foo = 'bar';

// New way (sandboxed)
	var foo = 'bar';

These two methods run the same code and achieve the same end, but the second example is sandboxed because we say it has “functional scope” and not “global scope”.


Function declaration vs. function literal

Function hoisting