diff bw formdata.set and formdata.append code example

Example: diff bw formdata.set and formdata.append

The difference between set() and FormData. 
append is that if the specified key does already exist, 
set() will overwrite all existing values with the new one, 
whereas FormData. append will 
append the new value onto the end of the existing set of values.
Note: This method is available in Web Workers.