You can use regex replace for that:

function removeLastDot(value) {
  return value.replace(/\.*$/, '')
}

console.log(removeLastDot('1..'))
console.log(removeLastDot('1.2.'))

In the example I use \.*$ regex:

• $ - means that I want replace at the end of string
• \.* - means that I want to match any number for . symbol (it is escaped cause . is special symbol in regex)

You can traverse the string with forEach and store the last index of any number in a variable. Then slice up to that variable.

let lastDigitIndex = 0;
for (let i = 0; i < str.length; i++) {
   let c = str[i];
   if (c >= '0' && c <= '9') lastDigitIndex = i;
};
console.log(str.slice(0, lastDigitIndex-1));

This will be an optimal solution.

Add replace(/\.*$/g, '') to match one or more dots at the end of the string.

So your code would be like this:

var maskedNumberValue = $(maskedNumber).val().replace(/[^0-9.]/g, '').replace('.', 'x').replace('x', '.').replace(/[^\d.-]/g, '').replace(/\.*$/g, '');