Recognizing numbers from strings in node.js

Question

How could I do it in Node.js to recognize if a string is a valid number?

Here are some examples of what I want:

"22"     => true
"- 22"   => true
"-22.23" => true
"22a"    => false
"2a2"    => false
"a22"    => false
"22 asd" => false

I dont actually need to return "true" or "false", but I need an unequivocally way to distinguish them. It seems like isNaN isnt available in node.js...

score 0 · Answer 1 · edited May 23 '17 at 11:50

0

I use the method suggested in this answer:

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

edited May 23 '17 at 11:50

Community

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answered Oct 28 '13 at 23:06

Raffaele

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`isNaN` is not available in nodejs – Enrique Moreno Tent Oct 28 '13 at 23:19

OneOfOne · Answer 2 · 2013-10-28T23:12:21.430

0

You can use regexp for example :

function is_number(n) {
   return (/^-?\d[0-9.e]*$/).test(n);
}

edited Oct 28 '13 at 23:12

answered Oct 28 '13 at 23:07

OneOfOne

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score 0 · Accepted Answer · answered Oct 28 '13 at 23:20

0

isNaN() is definitely available in node.js.

!isNaN(+n)

The unary plus operator is my personal choice; won't catch your "- 22" example, but you could use !isNaN(+n.replace(/\s/g, "") to strip spaces.

answered Oct 28 '13 at 23:20

cjohn

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You are right. I dont know why it wasnt working before... thanks! – Enrique Moreno Tent Oct 28 '13 at 23:28
No problem. It should be noted that javascript thinks `+""` and `+[]` are 0. So this solution doesn't hold up under the very best garbage you throw at it. – cjohn Oct 29 '13 at 02:50

Recognizing numbers from strings in node.js

3 Answers3