This works, and log into console 2 since it calls the function passing 7 as value.
In the next line however
processArg = 2;
You are telling your program that now processArg is not a function anymore, is now the number 2.
processed = processArg(num);
In the final line you are trying to use processArg as a function, but it won’t work since now it’s the number 2, as you instructed your program in the line above.