Course-JavaScript/js-types-n-oop.js

/**********************************************************************
* 
* JavaScript types and objects
*
*
**********************************************************************/
//
// Types and objects
// =================
//
// 	JavaScript's type system is split into two categories of enteties: 
// 	basic types or values and objects, they differ in several aspects.
//
// 						| values			| objects
// 		----------------+-------------------+--------------------------
// 		     mutability	| imutable			| mutable
// 		----------------+-------------------+--------------------------
// 		       identity	| equal values are 	| different objects
// 						| the same entity	| can have same 
// 						| (singletons)		| structure
// 		----------------+-------------------+--------------------------
//
//
// Basic values
// ------------
//
// numbers
	var integer = 123
	var floating_point = 3.1415
	var hex = 0xFF

// strings
	var string = 'string'
	var another_string = "also a string"
	var template = `
		a template string.
		this can include \\n's
		also summorts expansions ${ '.' }`

// boolieans
	var t = true
	var f = false

// nulls
	var n = null
	var u = undefined
	var not_a_number = NaN



// Values are in general:
//
// - singletons
	var a = 3.14
	var b = 3.14
	a === b // -> true

	// In general equal basic values are the same value and there is 
	// no way to create two copies of the same value.


// - imutable
	var a = 1
	var b = a

	// a and b hold the same value (1)
	a === b // -> true

	// now we update a...
	a += 1
	a === b // -> false
	// Note that we updated the value referenced by a, i.e. the old 
	// value (1) was not modified by the addition (b is still 1), 
	// rather a new value (2) was created and assigned to a.
	


// Equality and identity
//


// Automatic type coercion
//


// Type checking
//
	typeof(42) // -> 'number'
	typeof('meaning of life') // -> 'string'



// Objects
// -------
//

// Type cheking
//
// Here thesame approach as for simple types is not productive:

	typeof([42]) // -> 'object'
	typeof({}) // -> 'object'

// so a better approach would be to:

	[42] instanceof Array // -> true

// but since all objects are objects the test can get quite generic (XXX)

	[42] instanceof Object // -> true
	{} instanceof Object // -> true




// Prototypes and inheritance
//
//

// Constructors
//
//


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*                                                vim:set ts=4 sw=4 : */