With prefix Recipes
Recipes
Use prefixes to indicate things like currencies, area / phone country codes and etc.
There are two approaches to add prefix for masked input. Every approach has its own behaviour and requires basic understanding of different core concepts.
By pattern mask expression
This example demonstrates how to create prefix via dynamic pattern mask expression . Dollar symbol is a fixed character, which will be automatically added when user forgets to type it or deleted when user erase all digits.
By postprocessor
This example demonstrates how to create prefix via postprocessor . It provides more flexibility, and you can configure any desired behaviour. You can use built-in maskitoPrefixPostprocessorGenerator or create your own.
Don't forget that
mask property should be compatible with a new prefix! 
Maskito 