C#和JavaScript的区别

Strong and Loose Typing:

• 强弱比较

// C#

var customer = new Customer(); //var is compiler inferred



//Javascript

var customer = new Customer(); //var is variable declaration

C#：var变量由编译器决定合适的类型，此例为Customer类型

JavaScript：var代表变量的意思，没有类型的强制

• Compiler匹配最接近Type

//C#



var x = 0; // compiler暗示 to be int

bool isInt = x is int;  //x是int类型，右边是true

x = new object();  //C#定义过的变量需要保持typ

//Javascript



var x = 0; //creates variable x that holds a number

bool isNumber = typeof x == "number";  //works but limited

x = new object();  // no problem, can redefie the x with new type

• OO里的Strong typing：

//C#

class Dog : Animal, IMoveable {...}

class Car : Vehicle, IMoveable {...}



//Accept any animal (base class has Feed Methord)

void Feed(Animal ani) {ani.Feed();}





//Accept any object that implements interface

void Move(IMoveable object) {object.Move();}

Dog可以放入Feed方法，因为继承自animal

Dog和Car都可以放入Move方法，因为interface

//JavaScript



//Accept any object

//(must implement Feed function)

functionFeed(ani) {ani.Feed();}





//Accept any object 

//must implement move methord

function Move(object) {object.Move();}

 

不论是何种type的object只要其有Feed方法

Dynamic Typing:

即使定义过x对象，也可以随时增加其属性和方法。

Language Basics:

• 整体程序调用流程：

C#需要有一个入口程序，然后一步步的调用下去

Javascript是按照一行行执行下去，像Commond命令行

Language Closures:

在一个scope里x就一直可以用

Language Coalesce:

 

 

 

Javascript的基本元类型: 

1. Special Type：null & undefined

   //javascript
   
   
   
   var a = null;  //"null"
   
   var b = c;  //"undefined"

2. Value Type:

//JavaScript



var a = typeof 1;                //number

var b = typeof 1.0;              //number

var c = typeof true;            //true

var d = typeof false;            //false

var e = typeof "hello world"    //string

注意：type detector， 就象用as，is关键字在C#里

//javascript



var x = 1;

var typeName = typeof x;  //"number"

1.  Number Type:

 

special value