blocks|key|169079|text|检查变量是否等于四舍五入为整数的同一变量，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|169080|if(Math.round(data)+!=+data)+{
++++alert("Variable+is+not+an+integer!");
}|code-block|syntax|javascript|169081|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|$]]

Check if the variable is equal to that same variable rounded to an integer, like this:

<pre><code>if(Math.round(data) != data) {
 alert("Variable is not an integer!");
}
</code></pre>

blocks|key|169114|text|首先，NaN是一个“数字”(是的，我知道它很奇怪，就顺其自然吧)，而不是一个“函数”。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|169115|您需要检查变量的类型是否为数字，并且要检查整数，我将使用模数。|169116|alert(typeof+data+===+'number'+&&+data%251+==+0);|code-block|syntax|javascript|169117|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|$]]

First off, NaN is a "number" (yes I know it's weird, just roll with it), and not a "function".

You need to check both if the type of the variable is a number, and to check for integer I would use modulus.

<pre><code>alert(typeof data === 'number' &amp;&amp; data%1 == 0);
</code></pre>

blocks|key|169148|text|你可以检查这个数字是否有余数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|169149|var+data+=+22;

if(data+%25+1+===+0){
+++//+yes+it's+an+integer.
}|code-block|syntax|javascript|169150|请注意，如果您的输入也可以是文本，而您想先检查它不是文本，那么您可以先检查类型：|169151|var+data+=+22;

if(typeof+data+===+'number'){
+++++//+yes+it+is+numeric

++++if(data+%25+1+===+0){
+++++++//+yes+it's+an+integer.
++++}
}|169152|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|$]]

You could check if the number has a remainder:

<pre><code>var data = 22;

if(data % 1 === 0){
 // yes it's an integer.
}
</code></pre>

Mind you, if your input could also be text and you want to check first it is not, then you can check the type first:

<pre><code>var data = 22;

if(typeof data === 'number'){
 // yes it is numeric

 if(data % 1 === 0){
 // yes it's an integer.
 }
}
</code></pre>

blocks|key|387281|text|使用===运算符(strict+equality如下所示，|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|387282|if+(data+===+parseInt(data,+10))
++++alert("data+is+integer")
else
++++alert("data+is+not+an+integer")|code-block|syntax|javascript|387283|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Identity_strict_equality_(%2529)^0|9|F|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Use the === operator (<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Identity_strict_equality_()" rel="noreferrer">strict equality</a>) as below,

<pre><code>if (data === parseInt(data, 10))
 alert("data is integer")
else
 alert("data is not an integer")
</code></pre>

blocks|key|169263|text|假设您对有问题的变量一无所知，那么您应该采用这种方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|169264|if(typeof+data+===+'number')+{
++++var+remainder+=+(data+%25+1);
++++if(remainder+===+0)+{
++++++++//+yes,+it+is+an+integer
++++}
++++else+if(isNaN(remainder))+{
++++++++//+no,+data+is+either:+NaN,+Infinity,+or+-Infinity
++++}
++++else+{
++++++++//+no,+it+is+a+float+(still+a+number+though)
++++}
}
else+{
++++//+no+way,+it+is+not+even+a+number
}|code-block|syntax|javascript|169265|简单地说：|169266|if(typeof+data==='number'+&&+(data%251)===0)+{
++++//+data+is+an+integer
}|169267|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|$]]

Assuming you don't know anything about the variable in question, you should take this approach:

<pre><code>if(typeof data === 'number') {
 var remainder = (data % 1);
 if(remainder === 0) {
 // yes, it is an integer
 }
 else if(isNaN(remainder)) {
 // no, data is either: NaN, Infinity, or -Infinity
 }
 else {
 // no, it is a float (still a number though)
 }
}
else {
 // no way, it is not even a number
}
</code></pre>

To put it simply:

<pre><code>if(typeof data==='number' &amp;&amp; (data%1)===0) {
 // data is an integer
}
</code></pre>

blocks|key|169310|text|这取决于，你是否也想将字符串转换为潜在的整数？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|169311|这样就可以了：|169312|function+isInt(value)+{
++return+!isNaN(value)+&&+
+++++++++parseInt(Number(value))+==+value+&&+
+++++++++!isNaN(parseInt(value,+10));
}|code-block|syntax|javascript|169313|使用逐位操作|169314|简单的解析和检查|169315|function+isInt(value)+{
++var+x+=+parseFloat(value);
++return+!isNaN(value)+&&+(x+%7C+0)+===+x;
}|169316|短路和保存解析操作：|169317|function+isInt(value)+{
++if+(isNaN(value))+{
++++return+false;
++}
++var+x+=+parseFloat(value);
++return+(x+%7C+0)+===+x;
}|169318|或者可能两者都在一次拍摄中：|169319|function+isInt(value)+{
++return+!isNaN(value)+&&+(function(x)+{+return+(x+%7C+0)+===+x;+})(parseFloat(value))
}|169320|测试：|169321|isInt(42)++++++++//+true
isInt("42")++++++//+true
isInt(4e2)+++++++//+true
isInt("4e2")+++++//+true
isInt("+1+")+++++//+true
isInt("")++++++++//+false
isInt("++")++++++//+false
isInt(42.1)++++++//+false
isInt("1a")++++++//+false
isInt("4e2a")++++//+false
isInt(null)++++++//+false
isInt(undefined)+//+false
isInt(NaN)+++++++//+false|169322|这就是问题所在：http://jsfiddle.net/opfyrqwp/28/|offset|length|169323|性能|169324|测试表明，短路解决方案具有最佳性能(ops/sec)。|169325|//+Short-circuiting,+and+saving+a+parse+operation
function+isInt(value)+{
++var+x;
++if+(isNaN(value))+{
++++return+false;
++}
++x+=+parseFloat(value);
++return+(x+%7C+0)+===+x;
}|169326|这是一个基准测试：http://jsben.ch/#/htLVw|169327|如果你喜欢一种更短、更钝的短路形式：|169328|function+isInt(value)+{
++var+x;
++return+isNaN(value)+?+!1+:+(x+=+parseFloat(value),+(0+%7C+x)+===+x);
}|169329|当然，我建议让minifier来处理这件事。|169330|entityMap|0|LINK|mutability|MUTABLE|url|http://jsfiddle.net/opfyrqwp/28/|1|http://jsben.ch/#/htLVw^0|0|0|0|0|0|0|0|0|0|0|0|0|8|W|0|0|0|0|0|9|N|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|1V|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|1W|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|1X|8|@]|9|@]|A|$G|H]]|$1|O|3|P|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|Q|3|R|5|F|7|1Z|8|@]|9|@]|A|$G|H]]|$1|S|3|T|5|6|7|20|8|@]|9|@]|A|$]]|$1|U|3|V|5|F|7|21|8|@]|9|@]|A|$G|H]]|$1|W|3|X|5|6|7|22|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|F|7|23|8|@]|9|@]|A|$G|H]]|$1|10|3|11|5|6|7|24|8|@]|9|@$12|25|13|26|1|27]]|A|$]]|$1|14|3|15|5|6|7|28|8|@]|9|@]|A|$]]|$1|16|3|17|5|6|7|29|8|@]|9|@]|A|$]]|$1|18|3|19|5|F|7|2A|8|@]|9|@]|A|$G|H]]|$1|1A|3|1B|5|6|7|2B|8|@]|9|@$12|2C|13|2D|1|2E]]|A|$]]|$1|1C|3|1D|5|6|7|2F|8|@]|9|@]|A|$]]|$1|1E|3|1F|5|F|7|2G|8|@]|9|@]|A|$G|H]]|$1|1G|3|1H|5|6|7|2H|8|@]|9|@]|A|$]]|$1|1I|3|-4|5|6|7|2I|8|@]|9|@]|A|$]]]|1J|$1K|$5|1L|1M|1N|A|$1O|1P]]|1Q|$5|1L|1M|1N|A|$1O|1R]]]]

That depends, do you also want to cast strings as potential integers as well?

This will do:

<pre><code>function isInt(value) {
 return !isNaN(value) &amp;&amp; 
 parseInt(Number(value)) == value &amp;&amp; 
 !isNaN(parseInt(value, 10));
}
</code></pre>

<h3>With Bitwise operations</h3>

Simple parse and check

<pre><code>function isInt(value) {
 var x = parseFloat(value);
 return !isNaN(value) &amp;&amp; (x | 0) === x;
}
</code></pre>

Short-circuiting, and saving a parse operation:

<pre><code>function isInt(value) {
 if (isNaN(value)) {
 return false;
 }
 var x = parseFloat(value);
 return (x | 0) === x;
}
</code></pre>

Or perhaps both in one shot:

<pre><code>function isInt(value) {
 return !isNaN(value) &amp;&amp; (function(x) { return (x | 0) === x; })(parseFloat(value))
}
</code></pre>

Tests:

<pre><code>isInt(42) // true
isInt("42") // true
isInt(4e2) // true
isInt("4e2") // true
isInt(" 1 ") // true
isInt("") // false
isInt(" ") // false
isInt(42.1) // false
isInt("1a") // false
isInt("4e2a") // false
isInt(null) // false
isInt(undefined) // false
isInt(NaN) // false
</code></pre>

Here's the fiddle: <a href="http://jsfiddle.net/opfyrqwp/28/" rel="noreferrer">http://jsfiddle.net/opfyrqwp/28/</a>

<h3>Performance</h3>

Testing reveals that the short-circuiting solution has the best performance (ops/sec).

<pre><code>// Short-circuiting, and saving a parse operation
function isInt(value) {
 var x;
 if (isNaN(value)) {
 return false;
 }
 x = parseFloat(value);
 return (x | 0) === x;
}
</code></pre>

Here is a benchmark:
<a href="http://jsben.ch/#/htLVw" rel="noreferrer">http://jsben.ch/#/htLVw</a>

If you fancy a shorter, obtuse form of short circuiting:

<pre><code>function isInt(value) {
 var x;
 return isNaN(value) ? !1 : (x = parseFloat(value), (0 | x) === x);
}
</code></pre>

Of course, I'd suggest letting the minifier take care of that.

blocks|key|387404|text|您可以使用regexp来执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|387405|function+isInteger(n)+{
++++return+(typeof+n+==+'number'+&&+/%5E-?\d%2B$/.test(n%2B''));
}|code-block|syntax|javascript|387406|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 regexp for this:

<pre><code>function isInteger(n) {
 return (typeof n == 'number' &amp;&amp; /^-?\d+$/.test(n+''));
}
</code></pre>

blocks|key|169373|text|您可以使用此函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|169374|function+isInteger(value)+{
++++return+(value+==+parseInt(value));
}|code-block|syntax|javascript|169375|即使值是包含整数值的字符串，它也将返回true。|169376|因此，结果将是：|169377|alert(isInteger(1));+//+true
alert(isInteger(1.2));+//+false
alert(isInteger("1"));+//+true
alert(isInteger("1.2"));+//+false
alert(isInteger("abc"));+//+false|169378|entityMap^0|0|0|0|0|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]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

You could use this function:

<pre><code>function isInteger(value) {
 return (value == parseInt(value));
}
</code></pre>

It will return true even if the value is a string containing an integer value. 
So, the results will be:

<pre><code>alert(isInteger(1)); // true
alert(isInteger(1.2)); // false
alert(isInteger("1")); // true
alert(isInteger("1.2")); // false
alert(isInteger("abc")); // false
</code></pre>

blocks|key|387463|text|要检查整型是否像poster需要的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|387464|if+(%2Bdata===parseInt(data))+{return+true}+else+{return+false}|code-block|syntax|javascript|387465|注意数据前面的%2B(将字符串转换为数字)，===表示精确。|387466|下面是一些示例：|387467|data=10
%2Bdata===parseInt(data)
true

data="10"
%2Bdata===parseInt(data)
true

data="10.2"
%2Bdata===parseInt(data)
false|387468|entityMap^0|0|0|0|0|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]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

To check if integer like poster wants:

<pre><code>if (+data===parseInt(data)) {return true} else {return false}
</code></pre>

notice + in front of data (converts string to number), and === for exact.

Here are examples:

<pre><code>data=10
+data===parseInt(data)
true

data="10"
+data===parseInt(data)
true

data="10.2"
+data===parseInt(data)
false
</code></pre>

blocks|key|169434|text|来自http://www.toptal.com/javascript/interview-questions|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|169435|function+isInteger(x)+{+return+(x%5E0)+===+x;+}+|code-block|syntax|javascript|169436|我发现这是最好的方法。|169437|entityMap|0|LINK|mutability|MUTABLE|url|http://www.toptal.com/javascript/interview-questions^0|2|1G|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

From <a href="http://www.toptal.com/javascript/interview-questions" rel="nofollow">http://www.toptal.com/javascript/interview-questions</a>:

<pre><code>function isInteger(x) { return (x^0) === x; } 
</code></pre>

Found it to be the best way to do this.

blocks|key|169459|text|使用%7C运算符：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|169460|(5.3+%7C+0)+===+5.3+//+=>+false
(5.0+%7C+0)+===+5.0+//+=>+true|code-block|syntax|javascript|169461|因此，测试函数可能如下所示：|169462|var+isInteger+=+function+(value)+{
++if+(typeof+value+!==+'number')+{
++++return+false;
++}

++if+((value+%7C+0)+!==+value)+{
++++return+false;
++}

++return+true;
};|169463|entityMap^0|2|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

Use the <code>|</code> operator:

<pre><code>(5.3 | 0) === 5.3 // =&gt; false
(5.0 | 0) === 5.0 // =&gt; true
</code></pre>

So, a test function might look like this:

<pre><code>var isInteger = function (value) {
 if (typeof value !== 'number') {
 return false;
 }

 if ((value | 0) !== value) {
 return false;
 }

 return true;
};
</code></pre>

blocks|key|387561|text|您可以使用一个简单的正则表达式：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|387562|function+isInt(value)+{
++++var+er+=+/%5E-?[0-9]%2B$/;
++++return+er.test(value);
}|code-block|syntax|javascript|387563|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 a simple regular expression:

<pre><code>function isInt(value) {
 var er = /^-?[0-9]+$/;
 return er.test(value);
}
</code></pre>

blocks|key|169534|text|Number.isInteger()似乎是一条可行的道路。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|169535|MDN还为不支持Number.isInteger()的浏览器提供了以下polyfill，主要是所有版本的IE。|169536|Link+to+MDN+page|169537|Number.isInteger+=+Number.isInteger+%7C%7C+function(value)+{
++++return+typeof+value+===+"number"+&&+
+++++++++++isFinite(value)+&&+
+++++++++++Math.floor(value)+===+value;
};|code-block|syntax|javascript|169538|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger^0|0|I|0|8|I|0|0|G|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@$9|10|A|11|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|12|8|@]|D|@$9|13|A|14|1|15]]|E|$]]|$1|J|3|K|5|L|7|16|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

<code>Number.isInteger()</code> seems to be the way to go.

MDN has also provided the following polyfill for browsers not supporting <code>Number.isInteger()</code>, mainly all versions of IE.

<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger" rel="noreferrer">Link to MDN page</a>

<pre><code>Number.isInteger = Number.isInteger || function(value) {
 return typeof value === "number" &amp;&amp; 
 isFinite(value) &amp;&amp; 
 Math.floor(value) === value;
};
</code></pre>

blocks|key|169556|text|您可以使用regexp来完成此操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|169557|function+isInt(data){
++if(typeof(data)=='number'){
++++var+patt=/%5E[0-9e%2B]%2B$/;
++++data=data%2B"";
++++data=data.match(patt);
++++if(data==null){return+false;}
+++++else+{return+true;}}
++else{return+false;}+
}|code-block|syntax|javascript|169558|如果数据不是整数，它将返回false，否则返回true。|offset|length|style|CODE|169559|entityMap^0|0|0|D|5|N|4|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]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

You can use regexp to do this:

<pre><code>function isInt(data){
 if(typeof(data)=='number'){
 var patt=/^[0-9e+]+$/;
 data=data+"";
 data=data.match(patt);
 if(data==null){return false;}
 else {return true;}}
 else{return false;} 
}
</code></pre>

It will return <code>false</code> if data isn't an integer, <code>true</code> otherwise.

blocks|key|169631|text|对于不带分隔符的正整数值：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|169632|return+(+data+!==+''+&&+data+===+data.replace(/\D/,+'')+);|code-block|syntax|javascript|169633|测试1.如果不为空，2.如果value等于替换其值中的非数字字符的结果。|169634|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

For positive integer values without separators:

<pre><code>return ( data !== '' &amp;&amp; data === data.replace(/\D/, '') );
</code></pre>

Tests
1. if not empty and
2. if value is equal to the result of a replace of a non-digit char in its value.

blocks|key|387737|text|另外，Number.isInteger()。也许Number.isSafeInteger()是通过使用es6指定的here的另一个选项。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|387738|要在ES6之前版本的浏览器中polyfill+Number.isSafeInteger(..)：|387739|Number.isSafeInteger+=+Number.isSafeInteger+%7C%7C+function(num)+{
++++return+typeof+num+===+"number"+&&+
+++++++++++isFinite(num)+&&+
+++++++++++Math.floor(num)+===+num+&&
+++++++++++Math.abs(+num+)+<=+Number.MAX_SAFE_INTEGER;
};|code-block|syntax|javascript|387740|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isSafeInteger^0|3|I|O|M|1L|4|0|0|N|O|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|15|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

Besides, <code>Number.isInteger()</code>. Maybe <code>Number.isSafeInteger()</code> is another option <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isSafeInteger" rel="nofollow">here</a> by using the ES6-specified.

To polyfill <code>Number.isSafeInteger(..)</code> in pre-ES6 browsers:

<pre><code>Number.isSafeInteger = Number.isSafeInteger || function(num) {
 return typeof num === "number" &amp;&amp; 
 isFinite(num) &amp;&amp; 
 Math.floor(num) === num &amp;&amp;
 Math.abs( num ) &lt;= Number.MAX_SAFE_INTEGER;
};
</code></pre>

blocks|key|387790|text|为文本框添加类numOnly，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|387791|$(document).on("input",+".numOnly",+function(e)+{
++++this.value+=+this.value.replace(/[%5E0-9\$]/g,'');
++++if(this.value!=""){
++++++alert('Integer+Number.');
++++}else{
++++++alert('Not+an+Integer+Number.');
+++}
});|code-block|syntax|javascript|387792|它对我很有效..试试这个|387793|您可以使用keypres、keyup、keydown等来代替input。|387794|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]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Add class numOnly for the textbox,

<pre><code>$(document).on("input", ".numOnly", function(e) {
 this.value = this.value.replace(/[^0-9\$]/g,'');
 if(this.value!=""){
 alert('Integer Number.');
 }else{
 alert('Not an Integer Number.');
 }
});
</code></pre>

It works for me.. Try this one

You can use keypres,keyup,keydown etc., instead input.

blocks|key|169773|text|如果你的浏览器支持Number.isInteger()，那么它就是最好的方式，如果不支持，我认为有很多种方式可以实现：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|169774|function+isInt1(value){
++return+(value%5E0)+===+value
}|code-block|syntax|javascript|169775|或者：|169776|function+isInt2(value){
++return+(typeof+value+===+'number')+&&+(value+%25+1+===+0);+
}|169777|169778|function+isInt3(value){
++return+parseInt(value,+10)+===+value;+
}|169779|169780|function+isInt4(value){
++return+Math.round(value)+===+value;+
}|169781|现在我们可以测试结果了：|169782|var+value+=+1
isInt1(value)+++//+return+true
isInt2(value)+++//+return+true
isInt3(value)+++//+return+true
isInt4(value)+++//+return+true

var+value+=+1.1
isInt1(value)+++//+return+false
isInt2(value)+++//+return+false
isInt3(value)+++//+return+false
isInt4(value)+++//+return+false

var+value+=+1000000000000000000
isInt1(value)+++//+return+false
isInt2(value)+++//+return+true
isInt3(value)+++//+return+false
isInt4(value)+++//+return+true

var+value+=+undefined
isInt1(value)+++//+return+false
isInt2(value)+++//+return+false
isInt3(value)+++//+return+false
isInt4(value)+++//+return+false

var+value+=+'1'+//number+as+string
isInt1(value)+++//+return+false
isInt2(value)+++//+return+false
isInt3(value)+++//+return+false
isInt4(value)+++//+return+false|169783|所以，所有这些方法都是有效的，但是当数字非常大时，parseInt和%5E运算符就不能很好地工作。|169784|entityMap^0|9|I|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|16|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|17|8|@]|D|@]|E|$I|J]]|$1|O|3|L|5|6|7|18|8|@]|D|@]|E|$]]|$1|P|3|Q|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|R|3|L|5|6|7|1A|8|@]|D|@]|E|$]]|$1|S|3|T|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|U|3|V|5|6|7|1C|8|@]|D|@]|E|$]]|$1|W|3|X|5|H|7|1D|8|@]|D|@]|E|$I|J]]|$1|Y|3|Z|5|6|7|1E|8|@]|D|@]|E|$]]|$1|10|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|11|$]]

<code>Number.isInteger()</code> is the best way if your browser support it, if not, I think there are so many ways to go:

<pre><code>function isInt1(value){
 return (value^0) === value
}
</code></pre>

or:

<pre><code>function isInt2(value){
 return (typeof value === 'number') &amp;&amp; (value % 1 === 0); 
}
</code></pre>

or:

<pre><code>function isInt3(value){
 return parseInt(value, 10) === value; 
}
</code></pre>

or:

<pre><code>function isInt4(value){
 return Math.round(value) === value; 
}
</code></pre>

now we can test the results:

<pre><code>var value = 1
isInt1(value) // return true
isInt2(value) // return true
isInt3(value) // return true
isInt4(value) // return true

var value = 1.1
isInt1(value) // return false
isInt2(value) // return false
isInt3(value) // return false
isInt4(value) // return false

var value = 1000000000000000000
isInt1(value) // return false
isInt2(value) // return true
isInt3(value) // return false
isInt4(value) // return true

var value = undefined
isInt1(value) // return false
isInt2(value) // return false
isInt3(value) // return false
isInt4(value) // return false

var value = '1' //number as string
isInt1(value) // return false
isInt2(value) // return false
isInt3(value) // return false
isInt4(value) // return false
</code></pre>

So, all of these methods are works, but when the number is very big, parseInt and ^ operator would not works well.

blocks|key|387904|text|Lodash+https://lodash.com/docs#isInteger+(从4.0.0开始)具有检查变量是否为整数的功能：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|387905|_.isInteger(3);
//+→+true

_.isInteger(Number.MIN_VALUE);
//+→+false

_.isInteger(Infinity);
//+→+false

_.isInteger('3');
//+→+false|code-block|syntax|javascript|387906|entityMap|0|LINK|mutability|MUTABLE|url|https://lodash.com/docs#isInteger^0|7|X|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Lodash <a href="https://lodash.com/docs#isInteger" rel="nofollow">https://lodash.com/docs#isInteger</a> (since 4.0.0) has function to check if variable is an integer:

<pre><code>_.isInteger(3);
// → true

_.isInteger(Number.MIN_VALUE);
// → false

_.isInteger(Infinity);
// → false

_.isInteger('3');
// → false
</code></pre>

blocks|key|387915|text|if(Number.isInteger(Number(data))){
++++//-----
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|387916|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>if(Number.isInteger(Number(data))){
 //-----
}
</code></pre>

blocks|key|169940|text|如果value可能是字符串形式的整数，例如var+value+=+"23"，并且您希望它的计算结果为true，则可以尝试使用Number.isInteger(Number(value))。避免尝试Number.isInteger(parseInt(value))，因为这并不总是返回正确的值。例如，如果var+value+=+"23abc"和你使用parseInt实现，它仍然会返回true。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|169941|但是，如果您需要严格的整数值，那么Number.isInteger(value)可能可以做到这一点。|169942|entityMap^0|2|5|L|G|1E|4|1Q|V|2Q|X|47|J|4U|8|0|H|N|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]|$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|I|$]]

You could try<code>Number.isInteger(Number(value))</code> if <code>value</code> might be an integer in string form e.g <code>var value = "23"</code> and you want this to evaluate to <code>true</code>. Avoid trying <code>Number.isInteger(parseInt(value))</code> because this won't always return the correct value. e.g if <code>var value = "23abc"</code> and you use the <code>parseInt</code> implementation, it would still return true.

But if you want strictly integer values then probably <code>Number.isInteger(value)</code> should do the trick.

blocks|key|169961|text|尝试以下函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|169962|function+isInteger+(num)+{
++++return+num+==+parseInt(%2Bnum,10)++&&+!isNaN(parseInt(num));
}

console.log+(+isInteger(42));++++++++//+true
console.log+(+isInteger("42"));++++++//+true
console.log+(+isInteger(4e2));+++++++//+true
console.log+(+isInteger("4e2"));+++++//+true
console.log+(+isInteger("+1+"));+++++//+true
console.log+(+isInteger(""));++++++++//+false
console.log+(+isInteger("++"));++++++//+false
console.log+(+isInteger(42.1));++++++//+false
console.log+(+isInteger("1a"));++++++//+false
console.log+(+isInteger("4e2a"));++++//+false
console.log+(+isInteger(null));++++++//+false
console.log+(+isInteger(undefined));+//+false
console.log+(+isInteger(NaN));+++++++//+false++++
console.log+(+isInteger(false));+++++++//+false
console.log+(+isInteger(true));+++++++//+false
console.log+(+isInteger(Infinity));+++++++//+false|code-block|syntax|javascript|169963|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|$]]

Try the following function:

<pre><code>function isInteger (num) {
 return num == parseInt(+num,10) &amp;&amp; !isNaN(parseInt(num));
}

console.log ( isInteger(42)); // true
console.log ( isInteger("42")); // true
console.log ( isInteger(4e2)); // true
console.log ( isInteger("4e2")); // true
console.log ( isInteger(" 1 ")); // true
console.log ( isInteger("")); // false
console.log ( isInteger(" ")); // false
console.log ( isInteger(42.1)); // false
console.log ( isInteger("1a")); // false
console.log ( isInteger("4e2a")); // false
console.log ( isInteger(null)); // false
console.log ( isInteger(undefined)); // false
console.log ( isInteger(NaN)); // false 
console.log ( isInteger(false)); // false
console.log ( isInteger(true)); // false
console.log ( isInteger(Infinity)); // false
</code></pre>

blocks|key|388080|text|在经历了几次成功和失败之后，我想出了这个解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|388081|const+isInt+=+(value)+=>+{
++return+String(parseInt(value,+10))+===+String(value)
}|code-block|syntax|javascript|388082|我喜欢上面关于检查不是NaN的值并使用parseFloat的想法，但是当我在React基础设施中尝试它时，由于某种原因它不能工作。|388083|编辑:我发现了一种不使用字符串的更好的方法：|388084|var+isInt+=+function+(str)+{
++return+str+===+'0'+%7C%7C+!!~~str;
}|388085|我认为这是最简短的答案。也许是最有效率的，但我可能会被纠正。:)|388086|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

After few successes and failures, I came up with this solution:

<pre><code>const isInt = (value) =&gt; {
 return String(parseInt(value, 10)) === String(value)
}
</code></pre>

I liked the idea above of checking the value for not being NaN and use parseFloat, but when I tried it in React infrastructure it didn't work for some reason.

Edit:
I found a nicer way without using strings:

<pre><code>var isInt = function (str) {
 return str === '0' || !!~~str;
}
</code></pre>

I think it's the shortest answer. Maybe even the most efficient, but I could be stand corrected. :)

blocks|key|170027|text|var+x+=+1.5;
if(!isNaN(x)){
+console.log('Number');
+if(x+%25+1+==+0){
+++console.log('Integer');
+}
}else+{
+console.log('not+a+number');
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|170028|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>var x = 1.5;
if(!isNaN(x)){
 console.log('Number');
 if(x % 1 == 0){
 console.log('Integer');
 }
}else {
 console.log('not a number');
}
</code></pre>

blocks|key|388114|text|Ok得到了减号，原因没有描述我的例子，所以更多的例子：)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|388115|我使用正则表达式和test方法：|388116|var+isInteger+=+/%5E[0-9]\d*$/;

isInteger.test(123);+//true
isInteger.test('123');+//+true
isInteger.test('sdf');+//false
isInteger.test('123sdf');+//false

//+If+u+want+to+avoid+string+value:
typeof+testVal+!==+'string'+&&+isInteger.test(testValue);|code-block|syntax|javascript|388117|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|$]]

Ok got minus, cause didn't describe my example, so more examples:):

I use regular expression and test method:

<pre><code>var isInteger = /^[0-9]\d*$/;

isInteger.test(123); //true
isInteger.test('123'); // true
isInteger.test('sdf'); //false
isInteger.test('123sdf'); //false

// If u want to avoid string value:
typeof testVal !== 'string' &amp;&amp; isInteger.test(testValue);
</code></pre>

blocks|key|170086|text|为什么没有人提到Number.isInteger()？|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|170087|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger|170088|对我来说工作得很好，并且解决了NaN以数字开头的问题。|170089|entityMap|0|LINK|mutability|MUTABLE|url^0|8|I|0|0|2P|0|0|F|3|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@]|D|@$9|U|A|V|1|W]]|E|$]]|$1|H|3|I|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|G]]]]

Why hasnt anyone mentioned <code>Number.isInteger()</code> ?

<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger" rel="noreferrer">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger</a>

Works perfectly for me and solves the issue with the <code>NaN</code> beginning a number.

blocks|key|170099|text|您也可以这样尝试。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|170100|var+data+=+22;
if+(Number.isInteger(data))+{
++++console.log("integer");
+}else{
+++++console.log("not+an+integer");
+}|code-block|syntax|javascript|170101|或|170102|if+(data+===+parseInt(data,+10)){
++++console.log("integer");
}else{
++++console.log("not+an+integer");
}|170103|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|$]]

you can also try it this way 

<pre><code>var data = 22;
if (Number.isInteger(data)) {
 console.log("integer");
 }else{
 console.log("not an integer");
 }
</code></pre>

or

<pre><code>if (data === parseInt(data, 10)){
 console.log("integer");
}else{
 console.log("not an integer");
}
</code></pre>

blocks|key|388156|text|试着这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|388157|let+number+=+5;
if+(Number.isInteger(number))+{
++++//do+something
}|code-block|syntax|javascript|388158|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|$]]

Just try this:

<pre><code>let number = 5;
if (Number.isInteger(number)) {
 //do something
}
</code></pre>

blocks|key|388188|text|“被接受”的答案是错误的(正如下面的一些评论指出的那样)。此修改可以使其工作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|388189|if+(data.toString()+===+parseInt(data,+10).toString())
++++alert("data+is+a+valid+integer")
else
++++alert("data+is+not+a+valid+integer")|code-block|syntax|javascript|388190|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|$]]

The 'accepted' answer is wrong (as some comments below point out).
this modification can make it work:
<pre><code>if (data.toString() === parseInt(data, 10).toString())
 alert(&quot;data is a valid integer&quot;)
else
 alert(&quot;data is not a valid integer&quot;)
</code></pre>

blocks|key|388234|text|如果它是一个数字，这将输出|type|unstyled|depth|inlineStyleRanges|entityRanges|data|388235|if+(data+>=+0+%7C%7C+data+<=0){
++++++++++++console.log('its+a+number');
++++++++++}|code-block|syntax|javascript|388236|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|$]]

This will output if it is a number
<pre><code>if (data &gt;= 0 || data &lt;=0){
 console.log('its a number');
 }
</code></pre>

blocks|key|170171|text|答案里有这么多选项。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|170172|对于纯整数，isNaN可能很棘手，您仍然需要其他检查来使其过时。|offset|length|style|CODE|170173|IE没有正式支持Number.isInteger()+(大多数人不会在意，但也有落后者)。|170174|我最终自己写了一些东西：|170175|function+isInteger(valueToCheck)+{
++++return+typeof+valueToCheck+!==+'undefined'
++++++++&&+(valueToCheck+===+parseInt(valueToCheck,+10));
}|code-block|syntax|javascript|170176|测试|170177|let+undefinedValue;
const+testValues+=+[
++++1,
++++'',
++++undefinedValue,
++++1.1,
++++'1',
++++'1.1',
++++'1-2',
++++'bob',
++++false,
++++[],
++++[1],
++++{},
++++{foo:+1}
];

testValues.forEach(value+=>+{
++++console.log(`${value}+-+${isInteger(value)}`);
})|170178|结果：|170179|1+-+true
''+-+false
undefined+-+false
1.1+-+false
'1'+-+false
'1.1'+-+false
'1-2'+-+false
'bob'+-+false
false+-+false
[]+-+false
[1]+-+false
{}+-+false
{foo:+1}+-+false|170180|有些测试值是过度杀伤力，但它们的存在清楚地表明什么都不能通过。你可以在函数中省略未定义的检查，但我发现在JS中未定义的东西可能会很奇怪，所以我觉得在那里更安全。|170181|entityMap^0|0|6|5|0|8|I|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@$D|14|E|15|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|16|8|@$D|17|E|18|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|19|8|@]|9|@]|A|$]]|$1|L|3|M|5|N|7|1A|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@]|A|$]]|$1|S|3|T|5|N|7|1C|8|@]|9|@]|A|$O|P]]|$1|U|3|V|5|6|7|1D|8|@]|9|@]|A|$]]|$1|W|3|X|5|N|7|1E|8|@]|9|@]|A|$O|P]]|$1|Y|3|Z|5|6|7|1F|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|11|$]]

So many options in the answers.
<code>isNaN</code> can be tricky for pure integer and you still need other checks that make it obsolete. 
<code>Number.isInteger()</code> isn't officially supported in IE (most wont care but there are stragglers out there).
I ended up writing something myself:
<pre><code>function isInteger(valueToCheck) {
 return typeof valueToCheck !== 'undefined'
 &amp;&amp; (valueToCheck === parseInt(valueToCheck, 10));
}
</code></pre>
<h2>Test</h2>
<pre><code>let undefinedValue;
const testValues = [
 1,
 '',
 undefinedValue,
 1.1,
 '1',
 '1.1',
 '1-2',
 'bob',
 false,
 [],
 [1],
 {},
 {foo: 1}
];

testValues.forEach(value =&gt; {
 console.log(`${value} - ${isInteger(value)}`);
})
</code></pre>
Results:
<pre><code>1 - true
'' - false
undefined - false
1.1 - false
'1' - false
'1.1' - false
'1-2' - false
'bob' - false
false - false
[] - false
[1] - false
{} - false
{foo: 1} - false
</code></pre>
Some test values are overkill but their existence just shows clearly nothing gets through. You could possibly omit the undefined check in the function, but I find undefined things can be weird in JS so felt more secure it being there.

How do I check if a variable is an integer in JavaScript, and throw an alert if it isn't? I tried this, but it doesn't work:

<pre><code>&lt;html&gt;
 &lt;head&gt;
 &lt;script type="text/javascript"&gt;
 var data = 22;
 alert(NaN(data));
 &lt;/script&gt;
 &lt;/head&gt;
&lt;/html&gt;
</code></pre>

How to check if a variable is an integer in JavaScript?

如何在JavaScript中检查变量是否为整数，如果不是则抛出警报？我试过了，但不起作用：<html> <head> <script type="text/javascript"> var data = 22; alert(NaN(data)); ...

问如何在JavaScript中检查变量是否为整数？
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