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In the first screenshot I’m trying to process the line of code “: double 2 * ;” which is defining the function “double”. In the debugger supplied by Google Chrome’s dev tools I am tracking a few variables and objects using the “watch feature”. This is a pretty handy feature since it lets me hone in on variables and objects whose behavior I wish to see as I step through the program. I have also set a few breakpoints (all not seen in screenshot): one at the very start of process, one before process checks for the character “:”, and one before process checks for a “;”. Armed with these breakpoints and my watched variables I am able to see what my temporary_function_definition array (which holds the function defined between the : and ;) holds and how my user_words object (which shall hold the user defined functions for later calling) is updated after I step after the current line (which should push the first input after the : into my temporary_function_definition array). As you can see in the second screenshot the string “double” has been pushed into my tracked temporary_function_definition array which at the very least indicates that my program is starting to record my function in this temporary array. Also, you can notice in both screenshots that I have the vestige of my console.log approach to debugging which is much more tedious than the built in debugger.
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Redoing the lab in JavaScript was definitely much quicker than the first time around in C++. I was able to neatly redo most of my C++ design in JavaScript. I ended up avoiding a lot of string manipulation and opting to use arrays which led to neater readable code (and less headaches dealing with string manipulation). JavaScripts lack of types is tricky. I was definitely more on edge in keeping track of whether I was working with a string or number. Overall, in this lab I did not have to worry about types too much since I was mostly dealing with numbers, so it was nice to not have to declare the types of every variable and the types of the map. I did however run into trouble with JavaScript’s scoping of local variables; for instance, I wanted a variable to be local, so I simply instantiated the variable without “var” in the location I wanted it; this instantiation made this variable global which was very confusing when I called the same portion of code with the variable and I was obtaining strange values. I used a map (i.e. a dictionary) in JavaScript which is essentially what everything in JavaScript is: an object. I realized how simple it is to make a dictionary and have key values be a string and values be functions (i.e. they became the “methods” of my dictionary. Dynamic typing made it much smoother to write my code since I did not have to update my code whenever I decided to change design; however, having to be forced to statically type did give me a better understanding of what my code was doing and why it was not working. I still am a bit fuzzy on the idea of what a closure is, but as far as I understand it, it has to do with having a local variable in on function which can be accessed and modified by functions called within the original function’s scope.