blocks|key|1890622|text|将字符串转换为数字的方法是使用Number，而不是parseFloat。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1890623|Number('1234')+//+1234
Number('9BX9')+//+NaN|code-block|syntax|javascript|1890624|如果您喜欢速记，也可以使用一元加号运算符：|1890625|%2B'1234'+//+1234
%2B'9BX9'+//+NaN|1890626|在检查NaN时要小心(操作符===和!==在NaN中不能像预期的那样工作)。使用：|1890627|+isNaN(%2BmaybeNumber)+//+returns+true+if+NaN,+otherwise+false|1890628|entityMap^0|F|6|P|A|0|0|0|0|E|3|I|3|M|3|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|T|$]]

The way to convert a string to a number is with <code>Number</code>, not <code>parseFloat</code>.
<pre><code>Number('1234') // 1234
Number('9BX9') // NaN
</code></pre>
You can also use the unary plus operator if you like shorthand:
<pre><code>+'1234' // 1234
+'9BX9' // NaN
</code></pre>
Be careful when checking against NaN (the operator <code>===</code> and <code>!==</code> don't work as expected with <code>NaN</code>). Use:
<pre><code> isNaN(+maybeNumber) // returns true if NaN, otherwise false
</code></pre>

blocks|key|1890630|text|function+isNumber(value:+string+%7C+number):+boolean
{
+++return+((value+!=+null)+&&
+++++++++++(value+!==+'')+&&
+++++++++++!isNaN(Number(value.toString())));
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1890631|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>function isNumber(value: string | number): boolean
{
 return ((value != null) &amp;&amp;
 (value !== '') &amp;&amp;
 !isNaN(Number(value.toString())));
}
</code></pre>

blocks|key|1676848|text|您可以使用Number.isFinite()函数：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1676849|Number.isFinite(Infinity);++//+false
Number.isFinite(NaN);+++++++//+false
Number.isFinite(-Infinity);+//+false
Number.isFinite('0');+++++++//+false
Number.isFinite(null);++++++//+false

Number.isFinite(0);+++++++++//+true
Number.isFinite(2e64);++++++//+true|code-block|syntax|javascript|1676850|注意:全局函数isFinite()和后面的Number.isFinite()之间有很大的不同。在前者的情况下，字符串强制被执行-所以isFinite('0')+===+true而Number.isFinite('0')+===+false。|1676851|另外，请注意这在IE中是不可用的！|1676852|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isFinite^0|5|H|5|H|0|0|0|7|A|L|H|1U|M|2H|U|0|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|@$9|14|A|15|B|C]|$9|16|A|17|B|C]|$9|18|A|19|B|C]|$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|1C|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

You can use the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isFinite" rel="noreferrer"><code>Number.isFinite()</code></a> function:

<pre><code>Number.isFinite(Infinity); // false
Number.isFinite(NaN); // false
Number.isFinite(-Infinity); // false
Number.isFinite('0'); // false
Number.isFinite(null); // false

Number.isFinite(0); // true
Number.isFinite(2e64); // true
</code></pre>

Note: there's a significant difference between the global function <code>isFinite()</code> and the latter <code>Number.isFinite()</code>. In the case of the former, string coercion is performed - so <code>isFinite('0') === true</code> whilst <code>Number.isFinite('0') === false</code>.

Also, note that this is not available in IE!

blocks|key|1890740|text|答案很简单：(注意是否有空格&+null)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1890741|isNaN(%2B'111')+=+false;
isNaN(%2B'111r')+=+true;
isNaN(%2B'r')+=+true;
isNaN(%2B'')+=+false;+++
isNaN(null)+=+false;+++|code-block|syntax|javascript|1890742|https://codepen.io/CQCoder/pen/zYGEjxd?editors=1111|offset|length|1890743|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|1F|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|T|8|@]|9|@$I|U|J|V|1|W]]|A|$]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|H]]]]

Simple answer: (watch for blank &amp; null)

<pre><code>isNaN(+'111') = false;
isNaN(+'111r') = true;
isNaN(+'r') = true;
isNaN(+'') = false; 
isNaN(null) = false; 
</code></pre>

<a href="https://codepen.io/CQCoder/pen/zYGEjxd?editors=1111" rel="noreferrer">https://codepen.io/CQCoder/pen/zYGEjxd?editors=1111</a>

blocks|key|1890753|text|我这里的简单解决方案是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1890754|const+isNumeric+=+(val:+string)+:+boolean+=>+{
+++return+!isNaN(Number(val));
}

//+isNumberic("2")+=>+true
//+isNumeric("hi")+=>+false;|code-block|syntax|javascript|1890755|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|$]]

My simple solution here is:
<pre><code>const isNumeric = (val: string) : boolean =&gt; {
 return !isNaN(Number(val));
}

// isNumberic(&quot;2&quot;) =&gt; true
// isNumeric(&quot;hi&quot;) =&gt; false;
</code></pre>

blocks|key|1676745|text|我会选择一个现有的并且已经测试过的解决方案。例如，来自typescript中的rxjs：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1676746|function+isNumeric(val:+any):+val+is+number+%7C+string+{
++//+parseFloat+NaNs+numeric-cast+false+positives+(null%7Ctrue%7Cfalse%7C"")
++//+...but+misinterprets+leading-number+strings,+particularly+hex+literals+("0x...")
++//+subtraction+forces+infinities+to+NaN
++//+adding+1+corrects+loss+of+precision+from+parseFloat+(#15100)
++return+!isArray(val)+&&+(val+-+parseFloat(val)+%2B+1)+>=+0;
}|code-block|syntax|javascript|1676747|rxjs/isNumeric.ts|offset|length|1676748|不使用rxjs+isArray()函数，使用简化的类型：|1676749|function+isNumeric(val:+any):+boolean+{
++return+!(val+instanceof+Array)+&&+(val+-+parseFloat(val)+%2B+1)+>=+0;
}|1676750|您应该始终使用您的用例来测试这些功能。如果您有特殊的值类型，则此函数可能不是您的解决方案。You+can+test+the+function+here.|1676751|结果是：|1676752|enum+++++++++:+CardTypes.Debit+++:+true
decimal++++++:+10++++++++++++++++:+true
hexaDecimal++:+0xf10b++++++++++++:+true
binary+++++++:+0b110100++++++++++:+true
octal++++++++:+0o410+++++++++++++:+true
stringNumber+:+'10'++++++++++++++:+true

string+++++++:+'Hello'+++++++++++:+false
undefined++++:+undefined+++++++++:+false
null+++++++++:+null++++++++++++++:+false
function+++++:+()+=>+{}++++++++++:+false
array++++++++:+[80,+85,+75]++++++:+false
turple+++++++:+['Kunal',+2018]+++:+false
object+++++++:+{}++++++++++++++++:+false|1676753|正如您所看到的，如果您将此函数与枚举一起使用，则必须小心。|1676754|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/ReactiveX/rxjs/blob/master/src/internal/util/isNumeric.ts|1|https://repl.it/repls/YellowgreenSpatialLevel^0|0|0|0|H|0|0|0|0|19|V|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|18|8|@]|9|@$I|19|J|1A|1|1B]]|A|$]]|$1|K|3|L|5|6|7|1C|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|1D|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1E|8|@]|9|@$I|1F|J|1G|1|1H]]|A|$]]|$1|Q|3|R|5|6|7|1I|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|1J|8|@]|9|@]|A|$E|F]]|$1|U|3|V|5|6|7|1K|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1L|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|13]]|14|$5|Z|10|11|A|$12|15]]]]

I would choose an existing and already tested solution. For example this from rxjs in typescript: 

<pre class="lang-js prettyprint-override"><code>function isNumeric(val: any): val is number | string {
 // parseFloat NaNs numeric-cast false positives (null|true|false|"")
 // ...but misinterprets leading-number strings, particularly hex literals ("0x...")
 // subtraction forces infinities to NaN
 // adding 1 corrects loss of precision from parseFloat (#15100)
 return !isArray(val) &amp;&amp; (val - parseFloat(val) + 1) &gt;= 0;
}
</code></pre>

<a href="https://github.com/ReactiveX/rxjs/blob/master/src/internal/util/isNumeric.ts" rel="nofollow noreferrer">rxjs/isNumeric.ts</a>

Without rxjs isArray() function and with simplefied typings:

<pre class="lang-js prettyprint-override"><code>function isNumeric(val: any): boolean {
 return !(val instanceof Array) &amp;&amp; (val - parseFloat(val) + 1) &gt;= 0;
}
</code></pre>

You should always test such functions with your use cases. If you have special value types, this function may not be your solution.
<a href="https://repl.it/repls/YellowgreenSpatialLevel" rel="nofollow noreferrer">You can test the function here.</a>

Results are:

<pre><code>enum : CardTypes.Debit : true
decimal : 10 : true
hexaDecimal : 0xf10b : true
binary : 0b110100 : true
octal : 0o410 : true
stringNumber : '10' : true

string : 'Hello' : false
undefined : undefined : false
null : null : false
function : () =&gt; {} : false
array : [80, 85, 75] : false
turple : ['Kunal', 2018] : false
object : {} : false
</code></pre>

As you can see, you have to be careful, if you use this function with enums.

blocks|key|1890708|text|考虑到您的变量可以是字符串、数字或任何类型-对于Angular/Typescript中的完整数字(非浮点数)，您可以使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1890709|var+isFullNumber:+boolean+=+
++++Number.isInteger(Number(yourVariable))+&&+yourVariable+!==+null;|code-block|syntax|javascript|1890710|正如@tarrbal所指出的那样编辑--我们不能只使用：|1890711|Number.isInteger(yourVariable);|1890712|要证明这一点，请查看以下3个测试：|1890713|let+testVariables+=+[0,+1,+"0",+"1",+"A",+{},+-3,+0.1,+NaN,+null,+undefined];+

let+isFullNumber:+boolean;
let+ix:+number+=+1;
testVariables.forEach(v+=>+{
isFullNumber+=+Number.isInteger(v);+++++++++++++++++++++++++//+<---
console.log(ix%2B%2B,+':+',+v,+isFullNumber);
})

console.log('--------------');

ix+=+1;
testVariables.forEach(v+=>+{
isFullNumber+=+Number.isInteger(Number(v));+++++++++++++++++//+<---
console.log(ix%2B%2B,+':+',+v,+isFullNumber);
})

console.log('--------------');
ix+=+1;
testVariables.forEach(v+=>+{
isFullNumber+=+Number.isInteger(Number(v))+&&+v+!==+null;+++//+<---
console.log(ix%2B%2B,+':+',+v,+isFullNumber);
})|1890714|这3个结果：|1890715|1+++:+++++++0+++++++++++true
2+++:+++++++1+++++++++++true
3+++:+++++++0+++++++++++false+<-+would+expect+true
4+++:+++++++1+++++++++++false+<-+would+expect+true
5+++:+++++++A+++++++++++false
6+++:+++++++{}++++++++++false
7+++:+++++++-3++++++++++true
8+++:+++++++0.1+++++++++false
9+++:+++++++NaN+++++++++false
10++:+++++++null++++++++false
11++:+++++++undefined+++false
----------------------------
1+++:+++++++0+++++++++++true
2+++:+++++++1+++++++++++true
3+++:+++++++0+++++++++++true
4+++:+++++++1+++++++++++true
5+++:+++++++A+++++++++++false
6+++:+++++++{}++++++++++false
7+++:+++++++-3++++++++++true
8+++:+++++++0.1+++++++++false
9+++:+++++++NaN+++++++++false
10++:+++++++null++++++++true+<-+would+expect+false
11++:+++++++undefined+++false
----------------------------
1+++:+++++++0+++++++++++true
2+++:+++++++1+++++++++++true
3+++:+++++++0+++++++++++true
4+++:+++++++1+++++++++++true
5+++:+++++++A+++++++++++false
6+++:+++++++{}++++++++++false
7+++:+++++++-3++++++++++true
8+++:+++++++0.1+++++++++false
9+++:+++++++NaN+++++++++false
10++:+++++++null++++++++false
11++:+++++++undefined+++false|1890716|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

Considering that your variable could be string or number or any type - for full numbers (non-floats) in Angular/Typescript you can use:
<pre><code>var isFullNumber: boolean = 
 Number.isInteger(Number(yourVariable)) &amp;&amp; yourVariable !== null;
</code></pre>
Edited as pointed out by @tarrbal - we CANNOT use just:
<pre><code>Number.isInteger(yourVariable);
</code></pre>
To prove check out these 3 tests:
<pre><code>let testVariables = [0, 1, &quot;0&quot;, &quot;1&quot;, &quot;A&quot;, {}, -3, 0.1, NaN, null, undefined]; 

let isFullNumber: boolean;
let ix: number = 1;
testVariables.forEach(v =&gt; {
isFullNumber = Number.isInteger(v); // &lt;---
console.log(ix++, ': ', v, isFullNumber);
})

console.log('--------------');

ix = 1;
testVariables.forEach(v =&gt; {
isFullNumber = Number.isInteger(Number(v)); // &lt;---
console.log(ix++, ': ', v, isFullNumber);
})

console.log('--------------');
ix = 1;
testVariables.forEach(v =&gt; {
isFullNumber = Number.isInteger(Number(v)) &amp;&amp; v !== null; // &lt;---
console.log(ix++, ': ', v, isFullNumber);
})
</code></pre>
and these 3 results:
<pre><code>1 : 0 true
2 : 1 true
3 : 0 false &lt;- would expect true
4 : 1 false &lt;- would expect true
5 : A false
6 : {} false
7 : -3 true
8 : 0.1 false
9 : NaN false
10 : null false
11 : undefined false
----------------------------
1 : 0 true
2 : 1 true
3 : 0 true
4 : 1 true
5 : A false
6 : {} false
7 : -3 true
8 : 0.1 false
9 : NaN false
10 : null true &lt;- would expect false
11 : undefined false
----------------------------
1 : 0 true
2 : 1 true
3 : 0 true
4 : 1 true
5 : A false
6 : {} false
7 : -3 true
8 : 0.1 false
9 : NaN false
10 : null false
11 : undefined false
</code></pre>

blocks|key|1890798|text|滚动浏览了每一个答案，并惊讶于这一简单的一行代码还没有出现：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1890799|const+isNumber+=+(val:+string+%7C+number)+=>+!!(val+%7C%7C+val+===+0)+&&+!isNaN(Number(val.toString()));|code-block|syntax|javascript|1890800|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|$]]

Scrolled through each answer and was surprised that this simple one-liner wasn't presented yet:
<pre><code>const isNumber = (val: string | number) =&gt; !!(val || val === 0) &amp;&amp; !isNaN(Number(val.toString()));
</code></pre>

blocks|key|1676789|text|大多数时候，我们要检查的值是字符串或数字，所以下面是我使用的函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1676790|const+isNumber+=+(n:+string+%7C+number):+boolean+=>+
++++!isNaN(parseFloat(String(n)))+&&+isFinite(Number(n));|code-block|syntax|javascript|1676791|1676792|Codesandbox+tests。|offset|length|1676793|const+willBeTrue+=+[0.1,+'1',+'-1',+1,+-1,+0,+-0,+'0',+"-0",+2e2,+1e23,+1.1,+-0.1,+'0.1',+'2e2',+'1e23',+'-0.1',+'+898',+'080']

const+willBeFalse+=+['9BX46B6A',+"%2B''",+'',+'-0,1',+[],+'123a',+'a',+'NaN',+1e10000,+undefined,+null,+NaN,+Infinity,+()+=>+{}]|1676794|entityMap|0|LINK|mutability|MUTABLE|url|https://codesandbox.io/s/cocky-shamir-kq6f6^0|0|0|0|0|H|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|X|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|Y|8|@]|9|@$J|Z|K|10|1|11]]|A|$]]|$1|L|3|M|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|N|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|O|$P|$5|Q|R|S|A|$T|U]]]]

Most of the time the value that we want to check is string or number, so here is function that i use:

<pre><code>const isNumber = (n: string | number): boolean =&gt; 
 !isNaN(parseFloat(String(n))) &amp;&amp; isFinite(Number(n));
</code></pre>

<hr>

<a href="https://codesandbox.io/s/cocky-shamir-kq6f6" rel="nofollow noreferrer">Codesandbox tests</a>.

<pre><code>const willBeTrue = [0.1, '1', '-1', 1, -1, 0, -0, '0', "-0", 2e2, 1e23, 1.1, -0.1, '0.1', '2e2', '1e23', '-0.1', ' 898', '080']

const willBeFalse = ['9BX46B6A', "+''", '', '-0,1', [], '123a', 'a', 'NaN', 1e10000, undefined, null, NaN, Infinity, () =&gt; {}]
</code></pre>

blocks|key|1676940|text|我的解决方案是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1676941|+function+isNumeric(val:+unknown):+val+is+string+%7C+number+{
++return+(
++++!isNaN(Number(Number.parseFloat(String(val))))+&&
++++isFinite(Number(val))
++);
}|code-block|syntax|javascript|1676942|//+true
isNumeric("-10");
isNumeric("0");
isNumeric("0xff");
isNumeric("0xFF");
isNumeric("8e5");
isNumeric("3.1415");
isNumeric("%2B10");
isNumeric("144");
isNumeric("5");

//+false
isNumeric("-0x42");
isNumeric("7.2acdgs");
isNumeric("");
isNumeric({});
isNumeric(NaN);
isNumeric(null);
isNumeric(true);
isNumeric(Infinity);
isNumeric(undefined);
isNumeric([]);
isNumeric("some+string");|1676943|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]]|$1|G|3|H|5|D|7|M|8|@]|9|@]|A|$E|F]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

My solution:
<pre><code> function isNumeric(val: unknown): val is string | number {
 return (
 !isNaN(Number(Number.parseFloat(String(val)))) &amp;&amp;
 isFinite(Number(val))
 );
}
</code></pre>
<pre><code>// true
isNumeric(&quot;-10&quot;);
isNumeric(&quot;0&quot;);
isNumeric(&quot;0xff&quot;);
isNumeric(&quot;0xFF&quot;);
isNumeric(&quot;8e5&quot;);
isNumeric(&quot;3.1415&quot;);
isNumeric(&quot;+10&quot;);
isNumeric(&quot;144&quot;);
isNumeric(&quot;5&quot;);

// false
isNumeric(&quot;-0x42&quot;);
isNumeric(&quot;7.2acdgs&quot;);
isNumeric(&quot;&quot;);
isNumeric({});
isNumeric(NaN);
isNumeric(null);
isNumeric(true);
isNumeric(Infinity);
isNumeric(undefined);
isNumeric([]);
isNumeric(&quot;some string&quot;);
</code></pre>

blocks|key|1676953|text|+const+isNumeric+=+(value:+string):+boolean+=>
++!new+RegExp(/[%5E\d]/g).test(value.trim());|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1676954|如果您希望允许使用小数点|unstyled|1676955|+++const+isNumeric+=+(value:+string):+boolean+=>
++++++!new+RegExp(/[%5E\d.]/g).test(value.trim());|1676956|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code> const isNumeric = (value: string): boolean =&gt;
 !new RegExp(/[^\d]/g).test(value.trim());
</code></pre>
If you want to allow decimal point
<pre><code> const isNumeric = (value: string): boolean =&gt;
 !new RegExp(/[^\d.]/g).test(value.trim());
</code></pre>

blocks|key|1676895|text|如果变量为sum=0；变量x；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1676896|那么，这个呢？sum%2B=(x%7C0)；|1676897|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

if
var sum=0;
var x;
then, what about this?
sum+=(x|0);

blocks|key|1890612|text|一个字符串是否可以被解析为一个数字是一个运行时的问题。Typescript不支持这种用例，因为它关注的是编译时(而不是运行时)的安全性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1890613|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Whether a string can be parsed as a number is a runtime concern. Typescript does not support this use case as it is focused on compile time (not runtime) safety.

In Typescript, this shows an error saying isNaN accepts only numeric values

<pre><code>isNaN('9BX46B6A')
</code></pre>

and this returns false because <code>parseFloat('9BX46B6A')</code> evaluates to <code>9</code>

<pre><code>isNaN(parseFloat('9BX46B6A'))
</code></pre>

I can still run with the error showing up in Visual Studio, but I would like to do it the right way.

Currently, I have written this modified function - 

<pre><code>static isNaNModified = (inputStr: string) =&gt; {
 var numericRepr = parseFloat(inputStr);
 return isNaN(numericRepr) || numericRepr.toString().length != inputStr.length;
}
</code></pre>

In Typescript, How to check if a string is Numeric

在Typescript中，这将显示一个错误，指出isNaN只接受数值isNaN('9BX46B6A')这将返回false，因为parseFloat('9BX46B6A')的计算结果为9isNaN(parseFloat('9BX46B6A'))我仍然可以在Visual Studio中显示错误，但我希望以正确的方式运行。目前，我已经编写了这个修改后的函数-static isNaNModified = 

问在Typescript中，如何检查字符串是否为数字
EN

回答 13

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问在Typescript中，如何检查字符串是否为数字EN

回答 13

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问在Typescript中，如何检查字符串是否为数字
EN