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Dynamic Regex for Decimal Precision not Working

I have the following hard-coded RegEx expression for decimal precision & scale, which works (in another project):
// This would be a Decimal(2,3)
var regex = /\d{0,2}(\.\d{1,3})?$/;
var result = regex.test(text);
However, I don't want to hard-code multiple variations. And, interestingly, the following fails...but I don't know why.
I "think" the concatenation may (somehow) be effecting the "test"
What am I doing wrong here?
SAMPLE:
var validationRules = {
decimal: {
hasPrecision: function (precision, scale, text) {
var regex = new RegExp('\d{0,' + precision + '}(\.\d{1,' + scale + '})?$');
var result = regex.test(text);
// result is ALWAYS true ????
alert(result);
alert(regex);
}
}
};
FAILING SAMPLE-SNIPPET:
$(document).ready(function () {
var validationRules = {
decimal: {
hasPrecision: function (precision, scale, text) {
var regex = new RegExp('\d{0,' + precision + '}(\.\d{1,' + scale + '})?$');
var result = regex.test(text);
alert(result);
alert(regex);
}
}
};
var masks = {
decimal: function (e) {
// TODO: get Kendo MaskedTextBox to run RegEx
var regex = new RegExp("^([0-9\.])$");
var key = String.fromCharCode(!event.charCode ? event.which : event.charCode);
if (!regex.test(key)) {
event.preventDefault();
return false;
}
}
};
var button = $('.btn');
var textbox = $('.txt');
textbox.on('keypress', masks.decimal);
button.on('click', function () {
var text = textbox.val();
validationRules.decimal.hasPrecision(2, 3, text);
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" value="1111" class="txt">
<input type="button" class="btn" value="Run it">

Always look at the result when building dynamic strings. In your case you're building it and just assuming it's turning into the REGEX pattern you want.
What you're actually building is, for example:
d{0,2}(.d{1,3})?$
Why? Because REGEX patterns built via the constructor (as opposed to literals) are built as strings - and in strings \ is interpreted as an escape character.
You, however, need these back slashes to persist into your pattern, so you need to double escape. In effect, you need to escape the escape so the final one is retained.
var regex = new RegExp('\\d{0,' + precision + '}(\\.\\d{1,' + scale + '})?$');
This will result in an equivalent of your hard-coded pattern assuming precision and scale contain the intergers you think they do. Check this too. (If they contain floats, for example, this will ruin your pattern.)
As for your false positives, this is probably down to a missing start-anchor instruction, i.e. ^.
/\d{0,2}(\.\d{1,3})?$/.test("1234"); //true
/^\d{0,2}(\.\d{1,3})?$/.test("1234"); //false, note ^

please try this I have implement on my project and it's working fine
const integer = Number(4)
const decimal=Number(2)
const reg = new RegExp(^[0-9]{0,${integer }}(\\.\\d[0-9]{0,${decimal- 1}})?$)
return value && !reg.test(value) ? Maximum length for integer is ${integer} and for decimal is ${decimal} : undefined;

When passing number with comma to text box why getElementById truncate the number after the comma

Please check this code :
function CalCPM()
{
var nv = document.getElementById('txtviews').value;
var nc = document.getElementById('txtcost').value;
var result =parseFloat(nc) / parseFloat(nv)/1000;
if(!isNaN(result))
{
document.getElementById('cpm').value = result.toFixed(4);
}
}
it work fine expect when you put comma in the number, means if you put in txtviews 1000000 and in txtcost 3000 you get a correct result that is 3.000
However if you use commas in any of the numbers then the problem starts, like
if you put in txtviews 1,000,000 and in txtcost 3,000
then the result will be 0.000003
OR if you start by putting value for txtcost first
then the result will be 3000.0000
which is not a correct value either way, any idea what is the problem??

I believe you'd have to strip them out, and then add them back in (the commas, that is)..
function CalCPM()
{
var nv = document.getElementById('txtviews').value.replace(',','');
var nc = document.getElementById('txtcost').value.replace(',','');
var result =parseFloat(nc) / parseFloat(nv)/1000;
if(!isNaN(result))
{
document.getElementById('cpm').value = Number(result).toLocaleString('en');
}
}

This can simply solve by using reg-ex :
function CalCPM()
{
var nv = (document.getElementById('txtviews').value).replace(/,/g,'');
var nc = (document.getElementById('txtcost').value).replace(/,/g,'');
var result =parseFloat(nc) / parseFloat(nv)/1000;
if(!isNaN(result))
{
document.getElementById('cpm').value = Number(result).toFixed(4);
}
}

Javascript wrong math [duplicate]

This question already has answers here:
Adding two numbers concatenates them instead of calculating the sum
(24 answers)
Closed 6 years ago.
I'm not sure what's wrong.
There are two variables, cena and uhrada. cena = 10 and uhrada = 279.8. I want to add them but I am getting 279.810 instead of 289.8.
Thanks for any help!
function priplatok(vstup1, vstup2) {
var chid = vstup1;
var cena = vstup2;
var uhrada = document.getElementById('uhr').value;
if (document.getElementById(chid).checked) {
var pridatu = uhrada + cena;
alert(pridatu);
}
}

The reason is that the values you take from the HTML input elements are always strings, even when they look like numbers. You have to first convert them, for instance with parseInt(...) or parseFloat():
var pridatu = parseFloat(uhrada) + parseFloat(cena);
A shorter way is to force conversion with a +:
var pridatu = +uhrada + +cena;
Although this is concise, you should probably first check if the input really is numeric. I refer to a popular question "Validate decimal numbers in JavaScript - IsNumeric()".

You get a string from document.getElementById('uhr').value.
If you want to do math, you need to cast the value either with parseInt(string, 10) or with parseFloat(string) to a number, implicit with a unary plus.
Your code:
function priplatok(vstup1, vstup2) {
var chid = vstup1;
var cena = vstup2;
var uhrada = +document.getElementById('uhr').value; // use implicit cast to number
if (document.getElementById(chid).checked) {
var pridatu = uhrada + cena;
alert(pridatu);
}
}

Thats because the values are strings and not numbers.
You have to make them numbers first and then calculate:
var pridatu = parseInt(uhrada) + parseInt(cena);

My VAT calculation is wrong

I'm trying to do a function for making a small calcul with vat.
So I have the following code:
<script type="text/javascript">
function calcdebours()
{
var taux = document.getElementById('debours_taux_tva').value;
var ht_no_tva = document.getElementById('debours_montant_ht_no_tva').value;
var ht_tva = document.getElementById('debours_montant_ht_tva').value;
var tva= Math.round((((ht_tva)*(taux))/100)*100)/100;
;
if(taux=='')
{
taux=0;
}
if(ht_no_tva=='')
{
ht_no_tva=0;
}
if(ht_tva=='')
{
ht_tva=0;
}
document.getElementById('debours_montant_tva').value = tva ;
document.getElementById('debours_montant_ttc').value = (tva) + parseInt(ht_tva)+ parseInt(ht_no_tva)
}
</script>
And below the fiddle:
http://jsfiddle.net/6zzRZ/
But for all it make the wrong calculation, I think it does not count the cent.
I've tried using just var 1 + var 2 but it just used to concatenate the number sor I use the parseInt function.
It has worked but the result is wrong for any kind of amount.
The trouble is that I tried parseDecimal but it say that this function does not exist.
Any kind of help will be much appreciated.

Try parseFloat. Or use the unitary + like this: var ht_no_tva = +document.getElementById('debours_montant_ht_no_tva').value; This gives JavaScript the hint that it should treat the value as a number.

Use parseFloat() instead of parseDouble:
http://www.w3schools.com/jsref/jsref_parsefloat.asp

Adding User input without rounding (Google Apps Script)

I am adding a users input in to UI as they add numbers and returning the results. The input is currency so I need to carry it out two decimals and not round.
Here is an example of my code:
function ceiling2(number) {
var ceiling2;
return ceiling2 = Math.ceil(number*100)/100;
}
//Totals
function lD23Total (e){
var app = UiApp.getActiveApplication();
var tB1v = parseInt(e.parameter.TextBox1);
var tB9v = parseInt(e.parameter.TextBox9);
var tB17v = parseInt(e.parameter.TextBox17);
var tB25v = parseInt(e.parameter.TextBox25);
var tB33v = parseInt(e.parameter.TextBox33);
var tB41v = parseInt(e.parameter.TextBox41);
var tB49v = parseInt(e.parameter.TextBox49);
var lD23 = app.getElementById("LabelD23").setStyleAttribute('fontWeight','bold');
var lD23T = tB1v + tB9v + tB17v + tB25v + tB33v + tB41v + tB49v;
lD23.setText("$ " + ceiling2(lD23T));
var app = UiApp.getActiveApplication();
app.close();
return app;
}
Currently it returns a rounded number.
I appreciate an suggestions you may offer!
Jon

The function parseInt() will convert the value to an integer, dropping the values after the decimal. Use parseFloat() instead.

I think your function is just fine...
if you remove the parseInt() and replace it either with parseFloat()as suggested by Eric or by Number() it should work...
if not then the problem might come from the way numbers are written:
If you used 26,4567 but you should use 26.4567 with a dot as separator in place of a comma.
Could you try and keep us informed ?
regards,
Serge
Or you can use this before sending to your function:
var newnumber=Number(number.toString().replace(",","."));// convert to string, replace comma with dot and set as number again.
and your function will work in both cases