Underscore在Coffeescript的控制台中不工作 [英] Underscore doesn't work in Coffeescript's console

问题描述

我刚刚开始使用Coffeescript和Coffeescript控制台，以及Underscore。但是，每当我定义一个函数，Coffeescript决定 _ 意味着该函数，似乎忘记了 _ = require'underscore' / code>。

为什么会发生这种情况？我如何防止它？

（我真的很喜欢将粘贴代码从我的文件复制到控制台。）

_ 在Coffeescript控制台中有一些特殊的含义吗？这意味着最后一个结果还是什么？这将解释我的问题？）

详情：

  $ coffee 
 coffee> _.contains [1，2，3]，3＃no Underscore，最初
 TypeError：不能调用未定义的方法'contains'
 at ... 
 coffee> 
 coffee> _ = require'underscore'
 {[Function] 
 _：[Circular]，
 VERSION：'1.3.3'，
 forEach： ... 
 
咖啡> _.contains [1，2，3]，3＃now Underscore工作正常
 true 
 coffee> 
 ------> someFunction =（a，b） - > ＃define a function ... 
 ......> a + b 
 
 [函数] 
咖啡> 
 coffee> _.contains [1，2，3]，3＃现在`_`不是Underscore了！ 
 TypeError：Object function（a，b）{＃``_`意思是最后结果还是sth？ 
 return a + b; 
}在eval.each上没有方法'contains'
。< anonymous>：3：7 Object.eval（/ usr / local / lib / node_modules / coffee-script / coffee-script.js：142：17）
 at interface。< anonymous> （/usr/local/lib/node_modules/coffee-script/lib/coffee-script/repl.js:131:40）
在Interface.emit（events.js：67：17）
 at Interface._onLine（readline.js：162：10）
在Interface._line（readline.js：426：8）
在Interface._ttyWrite（readline.js：603：14）
在ReadStream。< anonymous> （readline.js：82：12）
在ReadStream.emit（events.js：88：20）
在ReadStream._emitKey（tty.js：327：10）
 coffee> 
 coffee> _ = required'underscore'
 coffee> _.contains [1，2，3]，3＃现在都再好一会儿了
 true 
  

解决方案

CoffeeScript REPL具有这个JavaScript 的核心：

  try {
 _ = global._; 
 returnValue = CoffeeScript [eval]（_ =（+ code +\\\
），{
 filename：'repl'，
 modulename：'repl'
}）; 
 if（returnValue === void 0）{
 global._ = _; 
} 
 repl.output.write（+（inspectValue，false，2，enableColours））+\\\
）; 
} catch（err）{
 error（err）; 
} 
  

因此，如果最后一个命令返回了 _ 将是那个东西。我找不到任何有关这方面的文档，但搜索 _ 不是一个非常有效的活动。如果你想在CoffeeScript REPL中使用Underscore.js，你必须把它叫做 _ 。

感谢 Trevor Burnham （谁写了这本书，所以我想我们可以相信他的）我们知道CoffeeScript REPL使用 _ 作为最后的结果匹配 node.js REPL 的行为：

REPL功能

[...]

特殊变量 _

做同样的事情。

I've just started using Coffeescript and the Coffeescript console, and Underscore. However, whenever I define a function, Coffeescript decides that _ means that function, and seems to forget the initial assignment of _ = require 'underscore'.

Why does this happen? How can I prevent it?
(I'd really like to be able to copy paste code from my files into the console.)

(Does _ have some special meaning in the Coffeescript console? Does it mean "the last result" or something? That'd explain my issue?)

Details:

$ coffee 
coffee> _.contains [1, 2, 3], 3   # no Underscore, initially
TypeError: Cannot call method 'contains' of undefined
    at ...
coffee> 
coffee> _ = require 'underscore'
{ [Function]
  _: [Circular],
  VERSION: '1.3.3',
  forEach: [Function],
  ...

coffee> _.contains [1, 2, 3], 3    # now Underscore works fine
true
coffee> 
------> someFunction = (a, b) ->   # define a function ...
......>   a + b

[Function]
coffee> 
coffee> _.contains [1, 2, 3], 3     # now `_` is not Underscore any more!
TypeError: Object function (a, b) {    # Does `_` mean "last result" or sth?
  return a + b;
} has no method 'contains'
    at evalmachine.<anonymous>:3:7
    at Object.eval (/usr/local/lib/node_modules/coffee-script/lib/coffee-script/coffee-script.js:142:17)
    at Interface.<anonymous> (/usr/local/lib/node_modules/coffee-script/lib/coffee-script/repl.js:131:40)
    at Interface.emit (events.js:67:17)
    at Interface._onLine (readline.js:162:10)
    at Interface._line (readline.js:426:8)
    at Interface._ttyWrite (readline.js:603:14)
    at ReadStream.<anonymous> (readline.js:82:12)
    at ReadStream.emit (events.js:88:20)
    at ReadStream._emitKey (tty.js:327:10)
coffee> 
coffee> _ = require 'underscore'
coffee> _.contains [1, 2, 3], 3    # Now all is fine again, for a short while
true

解决方案

The CoffeeScript REPL has this JavaScript at its heart:

try {
  _ = global._;
  returnValue = CoffeeScript["eval"]("_=(" + code + "\n)", {
    filename: 'repl',
    modulename: 'repl'
  });
  if (returnValue === void 0) {
    global._ = _;
  }
  repl.output.write("" + (inspect(returnValue, false, 2, enableColours)) + "\n");
} catch (err) {
  error(err);
}

So if the last command returned something then _ will be that something. I can't find any documentation about this though but searching for _ isn't a terribly productive activity. If you want to use Underscore.js in the CoffeeScript REPL, you'll have to call it something other than _.

Thanks to Trevor Burnham (who wrote the book so I think we can trust him on this) we know that the CoffeeScript REPL uses _ as the last result to match the behavior of the node.js REPL:

REPL Features
[...]
The special variable _ (underscore) contains the result of the last expression.

Ruby's irb does the same thing.

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