javascript and test for number

Question

Possible Duplicate:
Is there a (built-in) way in JavaScript to check if a string is a valid number?

I am using JS in a riak map reduce job. I have a number I want to map and needs to be a number.

if I have a variable:

 var wp=sfggz5341&& or var=100

How can if test if number?

e.g.

if wp==Number:    
    OK 
else:    
    pass

possible duplicate of [Is there a (built-in) way in JavaScript to check if a string is a valid number?](http://stackoverflow.com/questions/175739/is-there-a-built-in-way-in-javascript-to-check-if-a-string-is-a-valid-number), [Check whether variable is number or string in javascript](http://stackoverflow.com/questions/1303646/check-whether-variable-is-number-or-string-in-javascript) — sachleen, Jan 24 '13 at 06:48

KooiInc · Answer 1 · 2013-01-24T06:50:44.247

2

You can test using: if (!isNaN(+wp)). In other words, convert the 'may be number' to number (using the + operator. If it can't be converted, the result is NaN. So !isNaN(...) means it's a number.

edited Jan 24 '13 at 06:50

answered Jan 24 '13 at 06:48

KooiInc

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score 2 · Accepted Answer · answered Jan 24 '13 at 06:48

2

You can use the typeof operator (see MDN for details):

var wp = "sfggz53141";
if (typeof wp === "number") {
    // number here
} else if (typeof wp === "string") {
    // string here
}

answered Jan 24 '13 at 06:48

jfriend00

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if `wp` is `'12345'`, `typeof wp` still would be `'string'` – KooiInc Jan 24 '13 at 07:19
@KooiInc - yes, because `'12345'` is a string, not a number. the OP asked if it `was` a number, not if it could be converted into a number. – jfriend00 Jan 24 '13 at 13:51

score 0 · Answer 3 · edited May 23 '17 at 10:34

You can either use isNaN() or isNumeric().

The isNumeric() can be used, but fails in following cases:

// Whitespace strings:
IsNumeric(' ') == true;
IsNumeric('\t\t') == true;
IsNumeric('\n\r') == true;

// Number literals:
IsNumeric(-1) == false;
IsNumeric(0) == false;
IsNumeric(1.1) == false;
IsNumeric(8e5) == false;

So the best way is:

function isNumber(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}

Reference: https://stackoverflow.com/a/1830844/462627

score -1 · Answer 4 · answered Jan 24 '13 at 06:49

-1

You can use !NaN(wp) to check if the string is a number.

answered Jan 24 '13 at 06:49

Blender

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score -1 · Answer 5 · answered Jan 24 '13 at 06:49

-1

try to use
isNaN()

This function returns true if the value is NaN, and false if not.

answered Jan 24 '13 at 06:49

Dnyan Waychal

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javascript and test for number

5 Answers5