How do I convert a string to an int in Javascript?

Question

how do I convert a string to int in JS, while properly handling error cases?

I want NaN returned when the argument is not really an integer quanityt:

• blank string should return NaN (not 0)
• mixed strings (e.g. "3b") should return NaN (not 3)

Answer 1

http://www.w3schools.com/jsref/jsref_parseInt.asp

Answer 2

function stringToInt(str) {
  var num = parseInt(str);
  if (num == str)
    return num;
  return NaN;
}

Examples

stringToInt("")
NaN

stringToInt("3")
3

stringToInt("3x")
Nan

Answer 3

var intval = /^\d+$/.test( strval ) ? parseInt( strval ) : NaN;

Answer 4

You don't need much- if s is a string:

s%1 will return 0 if s is an integer.

It will return a non-zero number if s is a non-integer number,

and NaN if s is not a number at all.

function isInt(s){
    return (s%1===0)? Number(s):NaN;
}

But although the number returned is an integer, to javascript it is still just a number.