Smooth CoffeeScript：探索服务器端JavaScript编程

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"Smooth CoffeeScript" 是一本介绍CoffeeScript编程的书籍，由E.Hoigaard基于Marijn Haverbeke的"Eloquent JavaScript"编写。本书深入浅出地讲解了CoffeeScript，这是一种借鉴了Python风格的JavaScript进化版，特别适合与Node.js一起用于服务器端开发。书中涵盖了基础语法、面向对象编程、函数式编程、搜索算法、模块化设计以及正则表达式等多个重要主题，旨在提升代码的清晰度、抽象性和可验证性。在"Language"部分，作者会介绍CoffeeScript的基础特性，如简洁的语法结构，它如何通过简化的语法糖来提高代码的可读性，以及它如何与JavaScript进行互译。CoffeeScript的语法通常比JavaScript更紧凑，例如，它用更少的字符实现同样的功能，如类的定义和函数的声明。 "Basic CoffeeScript"章节将引导读者了解CoffeeScript的基础知识，包括变量声明、条件语句、循环结构以及表达式处理。这些基础知识对于任何程序员来说都是至关重要的，它们构成了程序的基本逻辑结构。 "Functions"章节将深入探讨CoffeeScript中的函数，包括函数作为一等公民的概念，闭包，以及如何使用函数表达式和函数声明。函数在CoffeeScript中扮演着核心角色，是实现复杂逻辑和模块化设计的关键。 "Data Structures"章节会讲解CoffeeScript中的数组、对象以及它们的高级用法，如解构赋值和链式操作。数据结构的理解和有效使用是编写高效代码的基础。 "Error Handling"章节将涵盖异常处理，这是任何编程语言中必不可少的部分，帮助开发者编写健壮的代码，能正确处理可能出现的错误情况。 "Paradigm"章节会讨论CoffeeScript中的编程范式，包括命令式、声明式和函数式编程。CoffeeScript支持多种编程风格，使开发者可以根据项目需求选择最合适的编程方式。 "Functional Programming"章节会深入函数式编程的世界，介绍高阶函数、纯函数和函数组合等概念，这些都是CoffeeScript中实现无副作用、易于测试代码的重要工具。 "Searching"章节将讲解各种搜索算法，如线性搜索、二分查找等，这些算法是解决数据处理问题的基础。 "Object Orientation"章节将探讨面向对象编程，包括类的定义、继承和封装。CoffeeScript简化了JavaScript的面向对象模型，使得对象和类的创建更加直观。 "Regular Expressions"章节将介绍正则表达式在CoffeeScript中的应用，它是处理文本和字符串的强大工具，用于模式匹配和字符串操作。 "Modularity"章节将讨论模块化设计，这是大型项目组织和代码复用的关键。CoffeeScript提供了一种优雅的方式来组织和导入代码模块，以保持代码的清晰和可维护性。 "Appendix"部分包含了额外的语言特性、二叉堆（Binary Heaps）的介绍，以及关于性能优化和命令行工具的使用指南。此外，参考和索引部分提供了详细的语法参考和关键字索引，方便读者查找和回顾。 "Smooth CoffeeScript"是一本全面且深入的教程，适合想要掌握CoffeeScript的开发者，无论你是初学者还是经验丰富的程序员，都能从中受益。通过阅读这本书，你可以提升自己的编程技巧，学习如何利用CoffeeScript的特性编写出更优雅、更高效的代码。

Introduction

increment count by one every time the program has decided that it is not

11 yet. Here is the same program in CoffeeScript:

total = 0

count = 1

while count <= 10

total += count

count += 1

show total

This gives us a few more improvements. Most importantly, there is no

need to specify the way we want the program to jump back and forth any-

more. The magic word while takes care of that. It continues executing

the lines indented below it as long as the condition it was given holds:

count <= 10, which means ‘count is less than or equal to 10’. Appar-

ently, there is no need anymore to create a temporary value and compare

that to zero. This was a stupid little detail, and the power of programming

languages is that they take care of stupid little details for us.

This can also be expressed in a shorter form in CoffeeScript:

total = 0

total += count for count in [1..10]

show total

The for and in words goes through the range of numbers from 1 to 10

[1..10], assigning each number in turn to count. Each value in count is

then added to total.

Finally, here is what the program could look like if we happened to have

the convenient operation sum available, which computes the sum of a col-

lection of numbers similar to the mathematical notation

∑

n=1

show sum [1..10]

Another possibility is to have functions attached to datatypes. Here a sum

function is attached to an array, giving the sum of the elements in the array.

show [1..10].sum()

The moral of this story, then, is that the same program can be expressed

in long and short, unreadable and readable ways. The ﬁrst version of the

program was extremely obscure, while the last ones are almost English:

show the sum of the numbers from 1 to 10. (We will see in later chapters

how to build things like sum.)

Introduction

A good programming language helps the programmer by providing a more

abstract way to express himself. It hides uninteresting details, provides

convenient building blocks (such as the while construct), and, most of the

time, allows the programmer to add building blocks himself (such as the

sum operation).

◦ • ◦

JavaScript is the language that is, at the moment, mostly being used to do

all kinds of clever and horrible things with pages on the World Wide Web.

JavaScript is also used for scripting in a variety of applications and op-

erating systems. Of special note is server-side JavaScript (SSJS), where

the server portion of a web application is written in JavaScript, so a full

application can be expressed in one programming language. CoffeeScript

generates standard JavaScript code and can therefore be used in environ-

ments where standard JavaScript is accepted. It means that both browser

portions and server portions can be written in CoffeeScript.

CoffeeScript is a new language so it remains to be seen how popular it

becomes for general application development, but if you are interested in

programming, CoffeeScript is deﬁnitely a useful language to learn. Even

if you do not end up doing much web programming, the mind-bending

programs in this book will always stay with you, haunt you, and inﬂuence

the programs you write in other languages.

There are those who will say terrible things about JavaScript. Many of

these things are true. When I was for the ﬁrst time required to write some-

thing in JavaScript, I quickly came to despise the language. It would ac-

cept almost anything I typed, but interpret it in a way that was completely

different from what I meant. This had a lot to do with the fact that I did

not have a clue what I was doing, but there is also a real issue here: Java-

Script is ridiculously liberal in what it allows. The idea behind this design

was that it would make programming in JavaScript easier for beginners.

In actuality, it mostly makes ﬁnding problems in your programs harder,

because the system will not point them out to you.

However, the ﬂexibility of the language is also an advantage. It leaves

space for a lot of techniques that are impossible in more rigid languages,

and it can be used to overcome some of JavaScript’s shortcomings. After

learning it properly, and working with it for a while, I have really learned

to like this language. CoffeeScript repairs many of the confusing and cum-

bersome aspects of JavaScript, while keeping its underlying ﬂexibility and

beauty. It is doubleplusgood.

Basic CoffeeScript

in less straightforward ways, and it can be useful to ‘try them out’ on the

console to see what they produce.

This is what 144 looks like in bits

01000000 01100010 00000000 00000000 00000000 00000000 00000000 00000000

The number above has 64 bits. Numbers in CoffeeScript always do. This

has one important repercussion: There is a limited amount of different

numbers that can be expressed. With three decimal digits, only the num-

bers 0 to 999 can be written, which is 10

= 1000 different numbers. With

64 binary digits, 2

different numbers can be written. This is a lot, more

than 10

(a one with nineteen zeroes).

Not all whole numbers below 10

ﬁt in a CoffeeScript number though.

For one, there are also negative numbers, so one of the bits has to be used

to store the sign of the number. A bigger issue is that non-whole numbers

must also be represented. To do this, 11 bits are used to store the position

of the decimal dot within the number.

That leaves 52 bits

. Any whole number less than 2

, which is over 10

will safely ﬁt in a CoffeeScript number. In most cases, the numbers we

are using stay well below that, so we do not have to concern ourselves

with bits at all. Which is good. I have nothing in particular against bits,

but you do need a terrible lot of them to get anything done. When at all

possible, it is more pleasant to deal with bigger things.

Fractional numbers are written by using a dot.

9.81

For very big or very small numbers, one can also use ‘scientiﬁc’ notation

by adding an e, followed by the exponent of the number:

2.998e8

Which is 2.998 ·10

= 299 800 000.

Calculations with whole numbers (also called integers) that ﬁt in 52 bits

are guaranteed to always be precise. Unfortunately, calculations with frac-

tional numbers are generally not. Like π (pi) can not be precisely ex-

pressed by a ﬁnite amount of decimal digits, many numbers lose some

If you were expecting something like 10010000 here — good call, but read on.

CoffeeScript’s numbers are not stored as integers.

Actually, 53, because of a trick that can be used to get one bit for free. Look up the

‘IEEE 754’ format if you are curious about the details.

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