nullish2.js

function myFn(variable1, variable2) {
  variable2 ??= "default value"
  return variable1 + variable2
}

myFn("this has", " no default value") //returns "this has no default value"
myFn("this has no") //returns "this has no default value"
myFn("this has no", 0) //returns "this has no 0"

This function is debugged, please check my fork

Please, change var2 for variable2, cause the var2 doesn’t exist.

thanks @damianpumar, good catch! I've updated the code.