blocks|key|731199|text|是的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|731200|passwordNotEmpty+=+not+not+password|code-block|syntax|javascript|731201|或更短：|731202|passwordNotEmpty+=+!!password|731203|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Yup:

<pre><code>passwordNotEmpty = not not password
</code></pre>

or shorter:

<pre><code>passwordNotEmpty = !!password
</code></pre>

blocks|key|731251|text|它并不完全等价，但只有当email为非空并且具有非零的.length属性时，email?.length才为真。如果你对这个值执行not操作，那么对于字符串和数组，结果应该是你想要的那样。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|731252|如果email为null或没有.length，那么email?.length将计算为null，这是False值。如果它有一个.length，那么这个值将计算为它的长度，如果它是空的，它将是False值。|731253|您的函数可以实现为：|731254|eitherStringEmpty+=+(email,+password)+->
++not+(email?.length+and+password?.length)|code-block|syntax|javascript|731255|entityMap^0|C|5|R|7|12|D|1S|3|0|2|5|8|4|F|7|P|D|16|4|1Q|7|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]|$9|14|A|15|B|C]|$9|16|A|17|B|C]|$9|18|A|19|B|C]|$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|1C|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|1D|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|1E|8|@]|D|@]|E|$]]]|P|$]]

It isn't entirely equivalent, but <code>email?.length</code> will only be truthy if <code>email</code> is non-null and has a non-zero <code>.length</code> property. If you <code>not</code> this value the result should behave as you want for both strings and arrays.

If <code>email</code> is <code>null</code> or doesn't have a <code>.length</code>, then <code>email?.length</code> will evaluate to <code>null</code>, which is falsey. If it does have a <code>.length</code> then this value will evaluate to its length, which will be falsey if it's empty.

Your function could be implemented as:

<pre><code>eitherStringEmpty = (email, password) -&gt;
 not (email?.length and password?.length)
</code></pre>

blocks|key|731284|text|这是一个“真实”派上用场的案例。你甚至不需要为此定义一个函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|731285|test1+=+not+(email+and+password)|code-block|syntax|javascript|731286|为什么它会起作用？|731287|'0'+++++++//+true
'123abc'++//+true
''++++++++//+false
null++++++//+false
undefined+//+false|731288|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

This is a case where "truthiness" comes in handy. You don't even need to define a function for that:

<pre><code>test1 = not (email and password)
</code></pre>

Why does it work?

<pre><code>'0' // true
'123abc' // true
'' // false
null // false
undefined // false
</code></pre>

blocks|key|514931|text|如果您需要检查内容是否为字符串，而不是null，也不是数组，请使用简单类型的比较：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|514932|+if+typeof+email+isnt+"string"|code-block|syntax|javascript|514933|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you need to check that the content is a string, not null and not an array, use a simple typeof comparison:

<pre><code> if typeof email isnt "string"
</code></pre>

blocks|key|731386|text|下面是一个jsfiddle，它演示了一种非常简单的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|731387|简单地说，你只需使用javascript：|731388|var+email="oranste";
var+password="i";

if(!(email+&&+password)){
++++alert("One+or+both+not+set");++++++++
}
else{
++++alert("Both+set");+++
}|code-block|syntax|javascript|731389|在coffescript中：|731390|email+=+"oranste"
password+=+"i"
unless+email+and+password
++alert+"One+or+both+not+set"
else
++alert+"Both+set"|731391|希望这对某些人有帮助:)|731392|entityMap|0|LINK|mutability|MUTABLE|url|http://jsfiddle.net/Xd7qY/12/^0|5|8|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|13|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|C|$]]|$1|M|3|N|5|H|7|15|8|@]|9|@]|C|$I|J]]|$1|O|3|P|5|6|7|16|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]]]

Here is a <a href="http://jsfiddle.net/Xd7qY/12/" rel="nofollow">jsfiddle</a> demonstrating a very easy way of doing this.

Basicly you simply do this is javascript:

<pre><code>var email="oranste";
var password="i";

if(!(email &amp;&amp; password)){
 alert("One or both not set"); 
}
else{
 alert("Both set"); 
}
</code></pre>

In coffescript:

<pre><code>email = "oranste"
password = "i"
unless email and password
 alert "One or both not set"
else
 alert "Both set"
</code></pre>

Hope this helps someone :)

blocks|key|731442|text|我认为，如果某个事物存在，那么使用问号是在该事物上调用函数的最简单方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|731443|例如|731444|car+=+{
++tires:+4,
++color:+'blue'+
}|code-block|syntax|javascript|731445|你想要得到颜色，但前提是车存在...|731446|coffeescript：|731447|+car?.color|731448|翻译为javascript：|731449|if+(car+!=+null)+{
++car.color;
}|731450|它被称为存在运算符http://coffeescript.org/documentation/docs/grammar.html#section-63|offset|length|731451|entityMap|0|LINK|mutability|MUTABLE|url|http://coffeescript.org/documentation/docs/grammar.html#section-63^0|0|0|0|0|0|0|0|0|9|1U|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|15|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|17|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|18|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|19|8|@]|9|@]|A|$G|H]]|$1|O|3|P|5|6|7|1A|8|@]|9|@]|A|$]]|$1|Q|3|R|5|F|7|1B|8|@]|9|@]|A|$G|H]]|$1|S|3|T|5|6|7|1C|8|@]|9|@$U|1D|V|1E|1|1F]]|A|$]]|$1|W|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|13]]]]

I think the question mark is the easiest way to call a function on a thing if the thing exists.

for example

<pre><code>car = {
 tires: 4,
 color: 'blue' 
}
</code></pre>

you want to get the color, but only if the car exists... 

coffeescript:

<pre><code> car?.color
</code></pre>

translates to javascript:

<pre><code>if (car != null) {
 car.color;
}
</code></pre>

it is called the existential operator <a href="http://coffeescript.org/documentation/docs/grammar.html#section-63" rel="nofollow">http://coffeescript.org/documentation/docs/grammar.html#section-63</a>

blocks|key|515157|text|unless+email?+and+email
++console.log+'email+is+undefined,+null+or+""'|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|515158|首先使用存在运算符检查电子邮件是否未定义且不为空，如果知道存在，则只有在电子邮件字符串为空时，and+email部件才会返回false。|unstyled|offset|length|style|CODE|515159|entityMap^0|0|1B|9|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@$G|O|H|P|I|J]]|9|@]|A|$]]|$1|K|3|-4|5|F|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>unless email? and email
 console.log 'email is undefined, null or ""'
</code></pre>

First check if email is not undefined and not null with the existential operator, then if you know it exists the <code>and email</code> part will only return false if the email string is empty.

blocks|key|731624|text|根据关于检查变量是否有truthy值的this+answer，您只需要一行：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|731625|result+=+!email+or+!password|code-block|syntax|javascript|731626|您可以在此online+Coffeescript+console上亲自试用(&U)|731627|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/5515349/905801|1|http://larryng.github.io/coffeescript-repl/^0|B|6|J|B|0|0|0|5|R|1|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|H|7|12|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|13|8|@]|D|@$9|14|A|15|1|16]]|E|$]]|$1|M|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]|U|$5|P|Q|R|E|$S|V]]]]

Based on <a href="https://stackoverflow.com/a/5515349/905801">this answer</a> about checking if a variable has a <code>truthy</code> value or not , you just need one line:

<pre><code>result = !email or !password
</code></pre>

&amp; you can try it for yourself on this <a href="http://larryng.github.io/coffeescript-repl/" rel="nofollow noreferrer">online Coffeescript console</a>

blocks|key|515265|text|您可以使用以下命令代替接受的答案passwordNotEmpty+=+!!password|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|515266|passwordNotEmpty+=+if+password+then+true+else+false|code-block|syntax|javascript|515267|它给出了相同的结果(只是语法上的不同)。|515268|第一列是一个值，第二列是if+value的结果|515269|0+-+false
5+-+true
'string'+-+true
''+-+false
[1,+2,+3]+-+true
[]+-+true
true+-+true
false+-+false
null+-+false
undefined+-+false|515270|entityMap^0|G|T|0|0|0|C|8|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|O|3|P|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|Q|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|R|$]]

Instead of the accepted answer <code>passwordNotEmpty = !!password</code> you can use

<pre><code>passwordNotEmpty = if password then true else false
</code></pre>

It gives the same result (the difference only in syntax).

In the first column is a value, in the second is the result of <code>if value</code>:

<pre><code>0 - false
5 - true
'string' - true
'' - false
[1, 2, 3] - true
[] - true
true - true
false - false
null - false
undefined - false
</code></pre>

blocks|key|515327|text|您可以使用coffeescript+or=操作|type|unstyled|depth|inlineStyleRanges|entityRanges|data|515328|s+=+''++++
s+or=+null|code-block|syntax|javascript|515329|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can use the coffeescript or= operation

<pre><code>s = '' 
s or= null
</code></pre>

blocks|key|515400|text|我非常肯定@thejh的答案足以检查空字符串，但我认为我们经常需要检查‘它是否存在？’然后我们需要检查‘它是否为空?包括字符串，数组和对象’|type|unstyled|depth|inlineStyleRanges|entityRanges|data|515401|这是CoffeeScript执行此操作的简化方法。|515402|tmp?+and+and+Object.keys(tmp).length|code-block|syntax|javascript|515403|如果我们保持这个问题的顺序，它将被这个顺序检查:+1.它存在吗?+2.不是空字符串?+3.不是空对象？|515404|因此，即使在不存在的情况下，所有变量也不存在任何问题。|515405|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I'm pretty sure @thejh 's answer was good enough to check empty string BUT,
I think we frequently need to check that 'Does it exist?' and then we need to check 'Is it empty? include string, array and object'

This is the shorten way for CoffeeScript to do this.

<pre><code>tmp? and !!tmp and !!Object.keys(tmp).length
</code></pre>

If we keep this question order, that would be checked by this order
 1. does it exist?
 2. not empty string?
 3. not empty object?

so there wasn't any problems for all variable even in the case of not existed.

I've got this code that checks for the empty or null string. It's working in testing. 

<pre><code>eitherStringEmpty= (email, password) -&gt;
 emailEmpty = not email? or email is ''
 passwordEmpty = not password? or password is ''
 eitherEmpty = emailEmpty || passwordEmpty 

test1 = eitherStringEmpty "A", "B" # expect false
test2 = eitherStringEmpty "", "b" # expect true
test3 = eitherStringEmpty "", "" # expect true
alert "test1: #{test1} test2: #{test2} test3: #{test3}"
</code></pre>

What I'm wondering is if there's a better way than <code>not email? or email is ''</code>. Can I do the equivalent of C# <code>string.IsNullOrEmpty(arg)</code> in CoffeeScript with a single call? I could always define a function for it (like I did) but I'm wondering if there's something in the language that I'm missing.

Easiest way to check if string is null or empty

我有这段代码，用来检查空或null字符串。它在测试中起作用。eitherStringEmpty= (email, password) ->  emailEmpty = not email? or email is ''  passwordEmpty = not password? or password is ''  ...

问检查字符串是否为null或空的最简单方法
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