If statement if a value in a field changes

JavaScript
1

Need advice on how to write javascript based on the below logic.

I have a field that has a default value in it, and I want a result to occur based on if the default value in that field changes.

Field name: changeInContractDuration
Default value in field: 0 months

If anything other than 0 months appears in that field, the result changes to another field.

Make sense? Any advice appreciated!

2

What you are looking for is called an event listener. Look around for some information about event listeners and see how far that gets you.