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.

Possible duplicate of [Check if a number has a decimal place/is a whole number](http://stackoverflow.com/questions/2304052/check-if-a-number-has-a-decimal-place-is-a-whole-number) — Benny Bottema, Apr 14 '16 at 10:01

score 7 · Accepted Answer · answered Mar 23 '12 at 12:05

7

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

Or you could test

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

answered Mar 23 '12 at 12:05

stefan bachert

9,413
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That made the most sense to me. Thanks mate! – monkey blot Mar 23 '12 at 12:13
Sure, since javascript number is a double having about 15 digits precision. So you have to watch for numerical errors of certain result ranges – stefan bachert Sep 22 '17 at 15:21
1

What about "42.00". – V Maharajh Feb 23 '18 at 18:23

pimvdb · Answer 2 · 2012-03-23T12:14:15.787

5

You can use the % operator:

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

edited Mar 23 '12 at 12:14

answered Mar 23 '12 at 12:01

pimvdb

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But, I'm assuming that `result` is the already a number here as it's the result of the `sqrt()` function. I'm not sure you're solving what the OP asked. – jfriend00 Mar 23 '12 at 12:10
@jfriend00: Good catch. Then it's even more straight-forward to use the `%` operator I guess. – pimvdb Mar 23 '12 at 12:13

score 4 · Answer 3 · answered Mar 23 '12 at 12:01

4

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)

answered Mar 23 '12 at 12:01

James Hill

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1

+1 for using `.indexOf()` instead of a regex since it's simpler and faster than a regex for this particular problem. – jfriend00 Mar 23 '12 at 12:08

score 1 · Answer 4 · answered Mar 23 '12 at 12:00

1

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

answered Mar 23 '12 at 12:00

John Sobolewski

4,512
1
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Vatsal · Answer 5 · 2015-08-14T01:55:35.180

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 :)

score 0 · Answer 6 · answered Dec 10 '15 at 21:55

0

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");
}

answered Dec 10 '15 at 21:55

samar ranjan Nayak

101
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score 0 · Answer 7 · answered Sep 22 '22 at 18:58

I am sorry. This answer is too late. but I hope this will help.

function isThisDecimal(val){
  if (!(val.indexOf(".") == -1)){
    return true; // decimal 
  }
  return false; // number
}

console.log(isThisDecimal("12.00")); //true
console.log(isThisDecimal("12.12")); //true
console.log(isThisDecimal("12"));// false

check if number string contains decimal?

7 Answers7