In Typescript How to check if a string is Numeric

Question

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    gt        var numericRepr   parseFloat inputStr       return isNaN numericRepr     numericRepr toString   length    inputStr length

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if var sum 0  var x  then  what about this  sum   x 0

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Most of the time the value that we want to check is string or number  so here is function that i use   const isNumber    n  string   number   boolean   gt        isNaN parseFloat String n     amp  amp  isFinite Number n        Codesandbox tests   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

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Simple answer    watch for blank  amp  null   isNaN   111     false  isNaN   111r     true  isNaN   r     true  isNaN        false     isNaN null    false       https   codepen io CQCoder pen zYGEjxd editors 1111

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I would choose an existing and already tested solution  For example this from rxjs in typescript    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      rxjs isNumeric ts  Without rxjs isArray   function and with simplefied typings   function isNumeric val  any   boolean     return   val instanceof Array   amp  amp   val - parseFloat val    1   gt   0      You should always test such functions with your use cases  If you have special value types  this function may not be your solution  You can test the function here   Results are   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   As you can see  you have to be careful  if you use this function with enums

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function isNumber value  string   number   boolean      return   value    null   amp  amp              value          amp  amp              isNaN Number value toString

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My simple solution here is  const isNumeric    val  string    boolean   gt       return  isNaN Number val          isNumberic  quot 2 quot     gt  true    isNumeric  quot hi quot     gt  false

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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    quot 5700 quot   if  isNumeric val       alert  quot it is number   quot

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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

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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

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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

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For full numbers  non-floats  in Angular you can use   if  Number isInteger yourVariable

[typescript] In Typescript, How to check if a string is Numeric

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