Question

Using mootools I have a regex like this:

new RegExp('^([^\\D'+ separator +']+)(\\d{2})');

In a string it inserts the char defined in separator after every 2 characters. I want it to insert only for the last two.

Example:

 String     Result
 123456     12.34.56  // what it does now
 123456     1234.56   // what it should do

I don’t have much experience with regex so any help or link to a decent tutorial is appreciated.

Answer 1

Don’t use regex for this:

var str = "123456".split('').reverse().join('');
var x = str.substring(0,2) + '.' + str.substring(2);
var final = x.split('').reverse().join('');

console.log(final);

Live DEMO

Of course you can check if the string length is bigger than 2

if (str.length > 2)
    // ...

---

Or use string slice function:

str ="123456";
str.slice(0, -2) + "." + str.slice(-2);

How does it work?
I’ll break it into pieces:

// Start at the beginning of the string grab all the chars 
// and stop two chars before the end of the string
str.slice(0, -2)

// Start at two chars before the end of the string, take all the chars until  
// the  end of the string.
str.slice(-2);