Autofill value type text filed with string on certain event instead of user typing in the text field.

First of all thank you for such a nice editor,

My use case is as below.
In react js,
I want replace the existing text in the value text filed (Not key side) on any event instead of user typing the text in text filed.
But I am unable to find such event where I can replace or insert text in the value text filed from any string variable.
can you please suggest the way how to achieve this.

Thanks in advance !!!