Automatically copy data from one field to another

Summary

Automatically copy data from one field to another

Content

Hi,

We have a requirement to automatically duplicate/copy the value that is manually entered in one field, into another field. 

For eg, in ESS in Emergency Contact page, when a user fills in Legal First Name say 'ABC' of the contact, the Professional First Name field should automatically get populated with the same value 'ABC'. Is this possible through EL ? Can someone pls share a sample EL that I can try ?

Thank you very much !

Nitin