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

Here are efficient functions that check if the value is a number or can be safely converted to a number:

function isNumber(value) {
    if ((undefined === value) || (null === value)) {
        return false;
    }
    if (typeof value == 'number') {
        return true;
    }
    return !isNaN(value - 0);
}

And for integers (would return false if the value is a float):

function isInteger(value) {
    if ((undefined === value) || (null === value)) {
        return false;
    }
    return value % 1 == 0;
}

The efficiency here is that parseInt (or parseNumber) are avoided when the value already is a number. Both parsing functions always convert to string first and then attempt to parse that string, which would be a waste if the value already is a number.

Thank you to the other posts here for providing further ideas for optimization!