In the numeric entry widget underscore is allowed. Why this is happening?

Sasi,

Why are you trying to enter an underscore in the numeric entry widget? Is there a use case that you need an underscore with numbers?

Meghan

I am trying to do a validation. If I enter anything except a digit in the numeric widget it should throw an error. I wrote java script for that and If i use the base type as string it will work but when i choose a number it does not work. Since numeric entry widget doesn't allow any other special characters. Why is it allowing underscore? 

Java 8 allows underscores in numbers to make them more readable. I'd guess the widget is following suit e.g.

100_000_000 is the same as 100000000