blocks|key|706186|text|if+(!string)+{
++//+is+emtpy
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|706187|What+is+the+best+way+to+test+for+an+empty+string+with+jquery-out-of-the-box?|unstyled|offset|length|706188|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/1812245/what-is-the-best-way-to-test-for-an-empty-string-with-jquery-out-of-the-box^0|0|0|24|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|R|8|@]|9|@$G|S|H|T|1|U]]|A|$]]|$1|I|3|-4|5|F|7|V|8|@]|9|@]|A|$]]]|J|$K|$5|L|M|N|A|$O|P]]]]

<pre><code>if (!string) {
 // is emtpy
}
</code></pre>

<a href="https://stackoverflow.com/questions/1812245/what-is-the-best-way-to-test-for-an-empty-string-with-jquery-out-of-the-box">What is the best way to test for an empty string with jquery-out-of-the-box?</a>

blocks|key|706179|text|如果您知道string不是数字，则可以这样做：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|706180|if+(!string)+{
++.
++.
++.|code-block|syntax|javascript|706181|entityMap^0|5|6|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

If you know that <code>string</code> is not numeric, this will work:

<pre><code>if (!string) {
 .
 .
 .
</code></pre>

blocks|key|922698|text|你可以直接做|type|unstyled|depth|inlineStyleRanges|entityRanges|data|922699|if(!string)
{
++//...
}|code-block|syntax|javascript|922700|这将检查string中是否有未定义、null和空字符串。|offset|length|style|CODE|922701|entityMap^0|0|0|4|6|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

you can just do 

<pre><code>if(!string)
{
 //...
}
</code></pre>

This will check <code>string</code> for undefined, null, and empty string.

blocks|key|706249|text|需要明确的是，当theString是一个未声明的变量时，if(!theString){//...}将抛出一个未定义的错误，而不是发现它为真。另一方面，如果您有：if(!window.theString){//...}或var+theString;+if(!theString){//...}，它将按预期工作。在变量可能未声明的情况下(与属性或未设置的变量相反)，您需要使用：if(typeof+theString+===+'undefined'){//...}|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|706250|我的首选是创建一个原型函数，为您包装它。|706251|entityMap^0|S|L|28|S|31|10|57|17|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|I|$]]

To be clear, <code>if(!theString){//...}</code> where theString is an undeclared variable will throw an undefined error, not find it true. On the other hand if you have: <code>if(!window.theString){//...}</code> or <code>var theString; if(!theString){//...}</code> it will work as expected. In the case where a variable may not be declared (as opposed to being a property or simply not set), you need to use: <code>if(typeof theString === 'undefined'){//...}</code>

My preference is to create a prototype function that wraps it up for you.

blocks|key|922848|text|由于被标记为正确的答案包含一个小错误，下面是我最大的尝试来提出一个解决方案。我有两个选择，一个接受字符串，另一个接受字符串或数字，因为我假设很多人在javascript中混合使用字符串和数字。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|922849|步骤：-If对象为null它是一个null或空字符串。-If类型不是字符串(或数字)，它的字符串值为null或空。注意:我们可能也会在这里抛出一个异常，这取决于首选项。-If修剪后的字符串值的长度小于1。它为null或为空。|922850|var+stringIsNullOrEmpty+=+function(theString)
{
++++return+theString+==+null+%7C%7C+typeof+theString+!=+"string"+%7C%7C+theString.trim().length+<+1;
}

var+stringableIsNullOrEmpty+=+function(theString)
{
++++if(theString+==+null)+return+true;
++++var+type+=+typeof+theString;
++++if(type+!=+"string"+&&+type+!=+"number")+return+true;
++++return+theString.toString().trim().length+<+1;
}|code-block|syntax|javascript|922851|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Since the answer that is marked as correct contains a small error, here is my best try at coming up with a solution. I have two options, one that takes a string, the other takes a string or a number, since I assume many people are mixing strings and numbers in javascript.

Steps:
-If the object is null it is a null or empty string.
-If the type is not string (or number) it's string value is null or empty. NOTE: we might throw an exception here as well, depending on preferences.
-If the trimmed string value has a length that is small than 1 it is null or empty.

<pre><code>var stringIsNullOrEmpty = function(theString)
{
 return theString == null || typeof theString != "string" || theString.trim().length &lt; 1;
}

var stringableIsNullOrEmpty = function(theString)
{
 if(theString == null) return true;
 var type = typeof theString;
 if(type != "string" &amp;&amp; type != "number") return true;
 return theString.toString().trim().length &lt; 1;
}
</code></pre>

blocks|key|706437|text|你可以从逻辑上说出来|type|unstyled|depth|inlineStyleRanges|entityRanges|data|706438|假设您有一个名为strVal的变量，用于检查是否为null或空|706439|if+(typeof+(strVal)+==+'string'+&&+strVal.length+>+0)+
{
//+is+has+a+value+and+it+is+not+null++:)
}
else
{
//it+is+null+or+empty+:(
}|code-block|syntax|javascript|706440|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

you can say it by logic 

Let say you have a variable name a strVal, to check if is null or empty 

<pre><code>if (typeof (strVal) == 'string' &amp;&amp; strVal.length &gt; 0) 
{
// is has a value and it is not null :)
}
else
{
//it is null or empty :(
}
</code></pre>

blocks|key|922930|text|您可以创建一个Utility方法，该方法可以在许多地方重用，例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|922931|+function+isNullOrEmpty(str){
++++var+returnValue+=+false;
++++if+(++!str
++++++++%7C%7C+str+==+null
++++++++%7C%7C+str+===+'null'
++++++++%7C%7C+str+===+''
++++++++%7C%7C+str+===+'{}'
++++++++%7C%7C+str+===+'undefined'
++++++++%7C%7C+str.length+===+0+)+{
++++++++returnValue+=+true;
++++}
++++return+returnValue;
++}|code-block|syntax|javascript|922932|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 create one Utility method which can be reused in many places such as:

<pre><code> function isNullOrEmpty(str){
 var returnValue = false;
 if ( !str
 || str == null
 || str === 'null'
 || str === ''
 || str === '{}'
 || str === 'undefined'
 || str.length === 0 ) {
 returnValue = true;
 }
 return returnValue;
 }
</code></pre>

I want to try to do string call equivalent to the C# <code>String.IsNullOrEmpty(string)</code> in javascript. I looked online assuming that there was a simple call to make, but I could not find one. 

For now I am using a <code>if(string === "" || string === null)</code> statement to cover it, but I would rather use a predefined method (I keep getting some instances that slip by for some reason)

What is the closest javascript (or jquery if then have one) call that would be equal?

C# String.IsNullOrEmpty Javascript equivalent

我想尝试在javascript中执行相当于C# String.IsNullOrEmpty(string)的字符串调用。我在网上看了看，以为有一个简单的电话要打，但我找不到。现在，我使用if(string === "" || string === null)语句来覆盖它，但我更愿意使用预定义的方法(由于某些原因，我不断地得到一些实例)。最接近的javascript (或jquery，如果有)调用是什

问C# String.IsNullOrEmpty Javascript等效项
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回答 7

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