How to check if a number is decimal?

Question

Is there any way to know if a number is decimal, ie if it contains "comma"?;

One code I found was this:

Html

   <input type="text" onblur="isNumber(this.value)" id="text" />

Javascript

 function isNumber(text){  
     valor = parseFloat(text);  
     if ((!isNaN(valor))==false){
        alert("Por favor, não digite ...");}  
     return true;  
  }  

Via: http://scriptsexemplos.blogspot.com.br/2011/04/validar-se-um-numero-e-decimal.html

But it’s not working. To see how was click here

To summarize, I just want a condition that returns

true for: 5.69541 and

false for: 569.

Thank you.

Answer 1

If your number is in text format, the most guaranteed way to determine whether or not it is decimal is via a regex:

texto.match(/^-?\d+\.\d+$/);

That’s because I only use parseInt and parseFloat not enough - the text can get started with a number and contain other things afterwards:

parseInt("123abc");     // 123
parseFloat("123.4abc"); // 123.4

If your number is already in format Number, on the other hand, one can determine whether it is decimal by calculating the rest of the division by 1:

x % 1 != 0 && !isNaN(x % 1) // true se e somente se x é decimal

Integers always return zero as the rest of the division by 1, while fractional numbers return a non-zero value. NaN and Infinity return NaN.

Answer 2

If I understand correctly, you want a function that returns false for integers and non-numerical values, and true for broken numbers.

Something like that should work:

function isDecimal(num) {
    if(isNaN(num)) return false;             // false para não numéricos
    return parseInt(num) != parseFloat(num); // false para inteiros
}

The numbers need to be passed with a dot as a separator, not a comma. Ah, and throw away the code you found on the internet. It is a garbage, has at least 2 problems in 4 lines... At least the owner of the site admits that there is bad thing there :)

---

As requested, the same code rewritten using keys in the if:

function isDecimal(num) {
    if(isNaN(num)) { return false; }
    return parseInt(num) != parseFloat(num);
}

Or:

function isDecimal(num) {
    if(isNaN(num)) { 
        return false; 
    } else {
        return parseInt(num) != parseFloat(num);
    }
}

Or else:

function isDecimal(num) {
    return (parseInt(num) != parseFloat(num)) && !isNaN(num);
}