What is this

I come from C, Java, PHP background. I still code in JS on almost daily basis, but JS is sometimes quite cryptic and I don't really know what is going on.

This is notes on the characteristics of the Javascript language as I learn from "The secrets of the Javascript Ninja" by John Resig and watching other random tutorials on the web.

Functions

What's different about functions, coming from other world: function scope, what is this , anonymous functions, closure, apply, call

1. First-class objects

• Can be assigned to variables
• Passed as arguments to functions
• Returned as a function
• Can possess properties that can be dynamically created and assigned

2. Functions and variables Scope

• Variable declarations are thoroughly in scope from their point of declaration to the end of the function within which they’re declared, regardless of block nesting.
• hoisted : functions scope can be fast forward. E.g inside a function outter(), if innerHoistedFunc() is defined at the end of foo, it is still OK for foo to call innerHoistedFunc() right at beginning of foo()'s definition

3. "Physical" anatomy of a function

• arguments : Contains the arguments. It behaves exactly as an array (such as arguments.length and arguments.shift(), but internally not a JS array
• this : the context of the function when it is invoked, not when it is defined . See function invocation
• name : which is the literal string of function name. For anon functions, this is '' (empty string). Console.log(myfunc.name)

4. Some other characteristics

• 2 main types: named functions vs anonymous functions (a.k.a lambda sometimes)
• Self executing function (or immediate function) : functions which execute only once and immediately upon parsing. This is used in implementing a plugin : (function( bootstro, $, undefined ) {window.bootstro = window.bootstro || {}, jQuery)();
• Every top-level named function foo creates a window.foo reference. This is because window is like the global class
• Arguments passed can be redundant, ie. more than the number of actuall arguments declared.

5. Function invocation

• Functions can be invoked in 4 different ways
  • bar() : function
  • foo.bar() : method
  • apply
  • call

Event Loop & Callback Queue

Loop: Must watch video by Philip Roberts at EU JsConf 2014 : What the heck is an event loop anyway?

http://2014.jsconf.eu/speakers/philip-roberts-what-the-heck-is-the-event-loop-anyway.html

Queue: How are callbacks registered and maintained by Browser/jQuery