I get an error in my React app on clicking on links and by default when running it... can anyone help? What could be the problem?

Question

This error is displayed when running the react app using npm start:

enter image description here

Also whenever something is clicked, this error is displayed instead of performing the function. There is no "dd" named variable used or defined

dd is not defined

ReferenceError: dd is not defined
at IL (:1:188)
at :1:1713