Script ing

Wang_Wei@opi-corp.com

Content

1.Programming Paradigm 编程范式
2.Addressing 寻址、属性访问
3.Inheritance 继承
4.Scope 作用域
5.Closure 闭包
6.Embedding Script Engine 嵌入脚本引擎
7.JavaScript V8 Performance V8性能
8.Resources 一些链接和书籍

Benefits
•No compile, no build. Just Code and Test
•Very, very short design cycles
•Less code
•Absolute Flexibility.

让你的工作变得没那么枯燥，减少“体力活”
生成代码，瞬间产生大量代码，改善你的KPI数据....
扩展视野，给出更好的解决方案

Python Py2Exe
Script to Executable
Ruby Exerb
Compiler/Embeder
PHP Bambalam
Java GCJ
...

1.Programming Paradigm
http://en.wikipedia.org/wiki/Comparison_of_programming_paradigms

Imperative 各种语句直接改变程序状态，全局数据，共同的数据类型
ASM,C/C++/C#,Pascal,JavaScript...
Structured 代码缩进，N-S盒图，不使用GOTO（针对汇编语言）
C/C++/C#,Pascal,QB,JavaScript...
Procedural 局部变量,顺序执行，条件判断，循环迭代，模块化
C/C++/C#,Pascal,QB...
Event-driven 主循环，事件响应，异步
Win32SDK,Reactor Pattern:
Mina,Netty,Boost.Asio,Twisted,EventMachine
Browser DOM JavaScript
Automata-based 状态机，状态切换，状态表
Object-oriented 面向对象
C++,C#,Delphi,Python,Ruby,JavaScript,Lua....
Functional 函数式,匿名函数、delegate、lambda
Scheme,Erlang,OCaml,Haskell,JavaScript,Ruby,F#,C#4
Declarative 声明式，只描述计算的逻辑，不描述具体细节
XML,CSS,SQL,4GLs,Haskell,DSL,Effect Script,

1.Programming Paradigm
http://en.wikipedia.org/wiki/Comparison_
of_programming_paradigms

编程范式 Programming Paradigm
单个语言并不局限于某个范式

多范式编程语言 Multi-paradigm Programming Language
C++ : Procedural,Object-Oriented,Generic,Functional
C# : OO,Generic,Functional,Declarative
Ruby : Procedural,OO,Functional
JavaScript : OO,Functional

2.Addressing
Addressing
C/C++

寄存器寻址、

直接/间接内存寻
址

立即数

2.Addressing
Java

操作数栈

常量池

立即数

Virtual function and vftable
http://hi.baidu.com/aztack/blog/item/9258b2355545a088a71e124c.html

void main(int,char**)
{
C c; Disassemble...
c.i = 123;
c.f1();
}

{
C c;
c.i = 9;
c.f1();
}

“Object ” - {
properties C c;
c.i = 9;
c.f1();
}

“Object Reference” +
properties

this->f1();
“Function Object”
- socpe

goto page19

Virtual vs Non-Virtual
http://hi.baidu.com/aztack/blog/item/9258b2355545a088a71e124c.html

0x00401100
void f1(){...}
0x0012FF70 0x004060B0

0x004060B0 0x00401100 void f2(){...}

...... void f3(){...}

void f4(){...}

Stack Data Code

Fastes Function Call : Non-Virutal Add a layer of indirection to
Call 0x4111C2F implement Polymorphism

3.Prototype-based Inheritance
http://hi.baidu.com/aztack/blog/item/55ad0946b59268066a63e567.html
http://en.wikipedia.org/wiki/Prototype-based_programming

GrandChild Parent GrandParent

__proto__
grandChild = { parent = { parent = {
name:"Jack", name:"unnamed", name:"unnamed",
__proto__:parent
name="Jack" F4:function(){...}, F1:function(){...}
}; __proto__:grandParent F2:function(){...}
}; F3:function(){...}
};

grandChild.F3();

Self，JavaScript,Lua,ActionScript,Falcon,Io,Ioke,Object Lisp



__proto__ __proto__ __proto__
null
name="Jack" function F1()
name="unnamed"

function F2()
function F4()

????????? ???????? function F3()

grand_child.F3()
Prototype-Chain

Prototype-Chain to implement Prototype-based Inheritance



null
name="unnamed"

function F2()
function F4()

????????? ???????? function F3()

Hash Map

More layer of indirection to implement
Prototype-based Inheritance



null
name="unnamed"

function F2()
function F4()

????????? ???????? function F3()

Linked List Prototype-based inheritance
share properties & methods
while classic inheritance only
More layer of indirection to implement share methods
Prototype-based Inheritance

4.Scope

Function Declaration Function Expression
function f1(){...} function(){}

f1 function f1(){...} function (){...}

4.Scope - JavaScript has only function scope,nothing else

Entering Executing Context

Code Execution
Hoisting:
函数、变量声明提升到最开始

5.Closure
all parent scopes
- A closure is a combination of a function and statically saved

Stack-Oriented Programming Language
At return from a function,it's local variables are removed from stack

ESP
ESP

1.Not set to zero
2.Accessible in c/c++!
3.Results Undefined
behavior

5.Closure
all parent scopes

JavaScript anonymous Heap

VO

Variable Object data

local __parent__
variable

__parent__ Scope-Chain!!!
Function Object

Code
function(){
f [[Call]] this code with f() print(data.str);
}
goto page9

5.Closure
all parent scopes

def entryExit(f):
def new_f():
@entryExit
print "Entering", new_f.__name__
def someFunc:pass
f()
print "Exited", new_f.__name__
new_f.__name__ = f.__name__
return new_f

function entryExit(f){
function new_f(){
print("Entring",new_f.__name__);
f();
print("Exited",new_f.__name__);
} var f = entryExit(
new_f.__name__ = f.name; function(){...}
return new_f; );
}

Save function address and
function name

make a callable object with
operator()

consider number of
parameters and return type

Boost preprocessor
and
Variadic Templates to help

5.Closure
all parent scopes

A common mistake : Creating closures in loops

function setupHelp() {
var helpText = [
{'id': 'email', 'help': 'Your e-mail address'},
{'id': 'name', 'help': 'Your full name'},
{'id': 'age', 'help': 'Your age (you must be over 16)'}
];

for (var i = 0; i < helpText.length; i++) {
var item = helpText[i];
document.getElementById(item.id).onfocus = function() {
showHelp(item.help);
}
}
}
https://developer.mozilla.org/en/JavaScript/Guide/Closures

5.Closure
all parent scopes

Fix: Avoid creating unneccessary stuffs in loops

function setupHelp() {
var helpText = {
'email': 'Your e-mail address',
'name': 'Your full name',
'help': 'Your age (you must be over 16)'
};
function ShowHelp(){
alert(helpText[this.id]);
}
for (var id in helpText) {
document.getElementById(id).onfocus = showHelp
}
}

https://developer.mozilla.org/en/JavaScript/Guide/Closures

6.Embedding Script Engine

JavaScript V8 for C++ Chrome/Chromium/Node.js

•
•
•
•
执注创初
行册建始
脚变执化
本量行引
和环擎
函境可

(
数选

)

PaxScript for Delphi


JavaScript V8 for .Net
http://javascriptdotnet.codeplex.com/

IronRuby/IronPython for .Net
http://ironruby.net/ http://ironpython.net/

Lua,Ruby,Python,PHP,Java,TraceMonkey for C++

WoW SketchUp Firefox

JRuby,Jython,Rhino+BSF,Groovy,Scala...for Java

屠魔服务端龙之刃

7.JavaScript V8 Performance
http://code.google.com/apis/v8/design.html

•Fast Property Access

•Dynamic Machine Code Generation
point.x
=>
# ebx = the point object
cmp [ebx,<hidden class offset>],<cached hidden class>
jne <inline cache miss>
mov eax,[ebx, <cached x offset>]

Resources - people,books,links

Dmitry A. Soshnikov
http://dmitrysoshnikov.com

developer.mozilla.org

John Resig @mozilla
http://ejohn.org/
JavaScript Secrets Pro JavaScript


•ECMA-262-5th
•O'Reilly - Javascript - The Definitive Guide, 4th Edition
•Oreilly.High.Performance.JavaScript.Mar.2010
•Pro.JavaScript.Design.Patterns

•Professional.JavaScript.for.Web.Developers.2nd.Edition

Nicholas C. Zakas @yahoo

http://www.nczonline.net/


http://www.crockford.com

YUI blog
JavaScript
The Theory of the Dom
Advanced JavaScript
Browser Wars
Quality
JavaScript: The Good Stuff
The State of Ajax
The JSON Saga
Ajax Performance
The State and Future of JavaScript

Douglas Crockford @yahoo

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