In Typescript, How to check if a string is Numeric

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

isNaN('9BX46B6A')

and this returns false because parseFloat('9BX46B6A') evaluates to 9

isNaN(parseFloat('9BX46B6A'))

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 -

static isNaNModified = (inputStr: string) => {
    var numericRepr = parseFloat(inputStr);
    return isNaN(numericRepr) || numericRepr.toString().length != inputStr.length;
}

The way to convert a string to a number is with Number, not parseFloat.

Number('1234') // 1234
Number('9BX9') // NaN

You can also use the unary plus operator if you like shorthand:

+'1234' // 1234
+'9BX9' // NaN

Be careful when checking against NaN (the operator === and !== don't work as expected with NaN). Use:

 isNaN(+maybeNumber) // returns true if NaN, otherwise false

Update 2

This method is no longer available in rxjs v6

I'm solved it by using the isNumeric operator from rxjs library (importing rxjs/util/isNumeric

Update

import { isNumeric } from 'rxjs/util/isNumeric';

. . .

var val = "5700";
if (isNumeric(val)){
   alert("it is number !");
}

function isNumber(value: string | number): boolean
{
   return ((value != null) &&
           (value !== '') &&
           !isNaN(Number(value.toString())));
}

You can use the Number.isFinite() function:

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

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

Also, note that this is not available in IE!