JavaScript learning

30/04/2015 cheatsheet

1. Function and Variable

a. Declare function

var function_name = function(){
//Do something here
}

b. Declare variable

var variable_name = 123;

c. Reuse method

var function_namedA = function(){
    this.age = 123;
    Console.log(this.age);
}
var Bob = {
    age = 12;
}
Bob.function_namedA();
//The age of Bob changed from 12 to 123

#2. Object a. Make an object

// type 1
var object_name = {
	variable_name1 = 123;
    variable_name2 = 123;
}
// type 2
object  = new Object();
object.variable_name1 = 123;

b. Make constructor of an object

function Person(job, age){
    this.job = job;
    this.age = age;
}

c. Use constructor of an object

var Bob = new Person('engineer', 23);

d. Use variables of an object

//type 1
var a = object[var_name]
//type 2
var a = object.var_name

e. Private and public variables and function

private variables are declared with the var keyword inside the object, and can only be accessed by private functions and privileged methods.
private functions are declared inline inside the object’s constructor (or alternatively may be defined via var functionName=function(){...}) and may only be called by privileged methods (including the object’s constructor).
privileged methods are declared with this.methodName=function(){...} and may invoked by code external to the object.
public properties are declared with this.variableName and may be read/written from outside the object.
public methods are defined by Classname.prototype.methodName = function(){...} and may be called from outside the object.
prototype properties are defined by Classname.prototype.propertyName = someValue
static properties are defined by Classname.propertyName = someValue

var Person = function(job, age){
    //job and age are public variables
    this.job = job;
    this.age = age;
	//sex is private variable
	var sex = 'male';
	//printJob() is a public function
    this.printJob(){
	    Console.log(this.job);
	}
	//sayHello() is private function
	var sayHello = function(){
	    Console.log('Hello');
	}
}
Person.variable = 123; //variable is pointing to object named Person
Person.prototype.variable = 345; //variable is pointing to the function of object named Person

#3. Inheritance a.Inheritance object

var a = {a: 1};
// a ---> Object.prototype ---> null

var b = Object.create(a);
// b ---> a ---> Object.prototype ---> null
console.log(b.a); // 1 (inherited)

var c = Object.create(b);
// c ---> b ---> a ---> Object.prototype ---> null

var d = Object.create(null);
// d ---> null
console.log(d.hasOwnProperty);
// undefined, because d doesn't inherit from Object.prototype

#4. Notes

Keyword this, within a function, this refers to object which call the function.

Hexa's Blog

Hexa's Blog

JavaScript learning

1. Function and Variable