check if number string contains decimal?

Question

After doing a sqrt()

How can I be check to see if the result contains only whole numbers or not?

I was thinking Regex to check for a decimal - if it contains a decimal, that means it didn't root evenly into whole numbers. Which would be enough info for me.

but this code isnt working...

result = sqrt(stringContainingANumber);
decimal = new RegExp(".");
document.write(decimal.test(result)); 

I bet there's other ways to accomplish the same thing though.

Answer 1

. means any char. You have to quote the dot. "\."

Or you could test

if (result > Math.floor(result)) {
   // not an decimal
}

Answer 2

You can use the % operator:

result % 1 === 0;  // rest after dividing by 1 should be 0 for whole numbers

Answer 3

Use indexOf():

​var myStr = "1.0";
myStr.indexOf("."); // Returns 1

// Other examples
myStr.indexOf("1"); // Returns 0 (meaning that "1" may be found at index 0)
myStr.indexOf("2"); // Returns -1 (meaning can't be found)

Answer 4

"." has meaning in the regex syntax which is "anything" you need to escape it using "\."

Answer 5

If its a string we can just use split function and then check the length of the array returned. If its more than 1 it has decimal point else not :). This doesn't work for numbers though :(. Please see the last edit. It works for string as well now :)

function checkDecimal() {
    var str = "202.0";
    var res = str.split(".");
    alert(res.length >1);
    var str1 = "20";

    alert(str1.split(".").length>1);
 }

Hope it helps someone. Happy Learning :)

Answer 6

Are you looking for checking string containing decimal digits , you can try like this

var num = "123.677";
if (!isNaN(Number(num)) {
alert("decimal no");
}
else {
alert("Not a decimal number");
}