Regular expression for a decimal with a precision of 2 not working

Question

The below code is to validate any input of decimal type with a precision of 2.

function check() {
    var str = $('#txttest').val();
    var patt = new RegExp("^[0-9]+(\.[0-9]{1,2})?$");
    var res = patt.test(str);
    alert(res);
}

Valid examples:

12
12.00
12.00a
12a
a12
1a2.00

Failed Case:

In some cases, the function is returning wrong values, like 1a2.

Now, please suggest.

2 issues: 1) double the backslash or use a regex literal, 2) add a `$` at the end. Try `var patt = /^[0-9]+(\.[0-9]{1,2})?$/;` — Wiktor Stribiżew, Oct 05 '16 at 20:03
Well, you say all those cases under "Valid examples" are valid, but [only two match](https://regex101.com/r/zYcF4p/2). — Wiktor Stribiżew, Oct 05 '16 at 20:05
but in my sample application, all are working :( except the failed one, 1a2 — Sagnik Mukherjee, Oct 05 '16 at 20:08
Hi @WiktorStribiżew, i have replaced 'new RegExp("^[0-9]+(\.[0-9]{1,2})?$")' with '/^[0-9]+(\.[0-9]{1,2})?$/' and its working. could you please explain the reason . Thanks. — Sagnik Mukherjee, Oct 05 '16 at 20:11
`/^[0-9]+(\.[0-9]{1,2})?$/` is a RegExp literal, which is why it is working. Your quoted string is not working because inside quotes you need to escape your backslash: `new RegExp("^[0-9]+(\\.[0-9]{1,2})?$")`. — atheaos, Oct 05 '16 at 20:56

score 0 · Answer 1 · answered Oct 05 '16 at 20:06

0

Why don't you use JavaScript's toFixed() method?

answered Oct 05 '16 at 20:06

Razvan Zamfir

4,209
6
38
252

I want to validate the input. – Sagnik Mukherjee Oct 05 '16 at 20:09
@SagnikMukherjee so? Just check `Number(input) == Number(input).toFixed(2)` - if they match, then it was the same number by definition. Not much need for a regex. – VLAZ Oct 05 '16 at 20:10
Thanks. I will definitely try your solution. But my question is why the expression is failing. – Sagnik Mukherjee Oct 05 '16 at 20:13

Regular expression for a decimal with a precision of 2 not working

1 Answers1