How do I check that a number is float or integer?

Question

How to find that a number is float or integer?

1.25 --> float  
1 --> integer  
0 --> integer  
0.25 --> float

Answer 1

function int(a) {
  return a - a === 0 && a.toString(32).indexOf('.') === -1
}

function float(a) {
  return a - a === 0 && a.toString(32).indexOf('.') !== -1
}

You can add typeof a === 'number' if you want to exclude strings.

Answer 2

This maybe isn't as performant as the % answer, which prevents you from having to convert to a string first, but I haven't seen anyone post it yet, so here's another option that should work fine:

function isInteger(num) {
    return num.toString().indexOf('.') === -1;
}

Answer 3

Here's my code. It checks to make sure it's not an empty string (which will otherwise pass) and then converts it to numeric format. Now, depending on whether you want '1.1' to be equal to 1.1, this may or may not be what you're looking for.

var isFloat = function(n) {
    n = n.length > 0 ? Number(n) : false;
    return (n === parseFloat(n));
};
var isInteger = function(n) {
    n = n.length > 0 ? Number(n) : false;
    return (n === parseInt(n));
};

var isNumeric = function(n){

   if(isInteger(n) || isFloat(n)){
        return true;
   }
   return false;

};

Answer 4

!!(24%1) // false
!!(24.2%1) // true

Answer 5

check for a remainder when dividing by 1:

function isInt(n) {
   return n % 1 === 0;
}

If you don't know that the argument is a number you need two tests:

function isInt(n){
    return Number(n) === n && n % 1 === 0;
}

function isFloat(n){
    return Number(n) === n && n % 1 !== 0;
}

Answer 6

Any Float number with a zero decimal part (e.g. 1.0, 12.00, 0.0) are implicitly cast to Integer, so it is not possible to check if they are Float or not.