How can I check if a string is a float?

Question

I am passing in a parameter called value. I\'d like to know if value is a float. So far, I have the following:

if (!isNaN(value))
{
    alert(\'this is a num         


        

Answer 1

Following functions also check for format. E.g. JavaScript native parseInt and parseFloat functions also parse strings containing non numeric characters, and functions above have consequences of this.

// For example, following code will work
var n = parseInt('123asd');
n == 123

These functions will return false for such string.

function isFloat(val) {
    var floatRegex = /^-?\d+(?:[.,]\d*?)?$/;
    if (!floatRegex.test(val))
        return false;

    val = parseFloat(val);
    if (isNaN(val))
        return false;
    return true;
}

function isInt(val) {
    var intRegex = /^-?\d+$/;
    if (!intRegex.test(val))
        return false;

    var intVal = parseInt(val, 10);
    return parseFloat(val) == intVal && !isNaN(intVal);
}