Questions about passing an argument to the function with Loop Conditions

In fact, a much better method (and keeps user experience in mind) is to allow the user to set a value they want like this:

var upper = parseInt(prompt("Give me a number! I'm hungry!"));
var randomNumber = getRandomNumber(upper);
var guess;
var attempts = 0;

function getRandomNumber(upper) {
  return Math.floor( Math.random() * upper ) + 1;
}

while ( guess !== randomNumber ) {
  guess = getRandomNumber ( upper );
  attempts += 1;
}

document.write("<p>The random number was: " + randomNumber + "</p>");
document.write("<p>It took the computer " + attempts + " attempts to get it right</p>");

Anytime you are using a function, the variables that are declared in the function call only apply to that function. Things get really tricky whenever you declare variables outside of the function and have the same named ones inside a function call.

Precedence is always given to the same named variable inside a function call. What that means is that in your example:

var drink = "Iced Tea";

function goToCoffeeShop(drink) {
    alert( drink + ' is on the way!' );
}
goToCoffeeShop();
//Added extra alert to show that drink is still defined
alert(drink + ' is on the way!');

drink is undefined in the function because the compiler looks at the variable defined by the function and uses that for the variable within the function. Since drink was not defined when it was called, it is undefined. So, the first alert says "undefined is on the way!".

The second alert is going to use the variable drink defined outside of the function because you aren't calling any function for its value. So, the second alert will say "Iced Tea is on the way!".

Just remember that any time you declare a variable in a function call, it is only valid for that function! Its value cannot be used elsewhere in the code.

Does that help?

Another example is this:

function showme(upper) {
var upper = 10;
alert(upper);
}
showme(20);

Which value do you think this function will show: 10 or 20? Well, it is going to show you 10 because you declared a new variable called upper within the function and that takes precedence over the called variable.

So, order of precedence for same named variables in regards to values of variables in functions goes like this (from the one used first to last): Variable declared inside function -> Variable in function call -> Variable declared outside function.

Now, taking a look at your code:

var randomNumber = getRandomNumber(upper);

You are calling this function, so that means the compiler is trying to put the value of a variable named upper into the function getRandomNumber but since there is no variable named upper declared outside the function, it will pass in the value undefined.

I love helping, for whatever reason, so it's all good, John! lol But, I see what you're getting confused by. In this example, you really could leave off those upper values because you're using the value from the variable. But those are two very different references.

This one:

function getRandomNumber(upper) { // HERE
  return Math.floor( Math.random() * upper ) + 1;
}

uses whatever value you pass into it as a substitute for the word upper and has nothing to do with the variable upper. It makes the function more dynamic such that you could pass in any value you wanted instead of just that variable upper.

This one:

guess = getRandomNumber ( upper ); // AND HERE

is passing in the value of the variable upper into the function getRandomNumber.

If you really wanted to eliminate your confusion, call the variable something different in the function call like upperLimit so that it will all now read:

var upper = 2000;
var randomNumber = getRandomNumber(upper);
var guess;
var attempts = 0;

function getRandomNumber(upperLimit) { 
  return Math.floor( Math.random() * upperLimit ) + 1;
}

while ( guess !== randomNumber ) {
  guess = getRandomNumber ( upper ); // AND HERE
  attempts += 1;
}

document.write("<p>The random number was: " + randomNumber + "</p>");
document.write("<p>It took the computer " + attempts + " attempts to get it right</p>");

You can avoid confusing yourself by just using different variable names, but you should do some practicing with this code to solidify the difference in those variables.

What you did with that above code is not what was being done in the original code, just so you're aware. Did you copy and paste this from somewhere because in your comment for the computersGuessRange you mention that it is useless to create and use, which you are absolutely right. You probably notice that it now takes a factor of 100 times more tries for the computer to guess the number because the random number generated is from 0-10 but the guess variable can get a random number from 0-10,000! lol.

Just to reiterate the difference between these two again:

This upper is a variable with a defined value:

var upper = 2000;

This upper is merely a placeholder for values that are passed into the function. It has no correlation to the variable upper:

function getRandomNumber(upper) { 
  return Math.floor(Math.random() * upper) + 1;
}

LOL..... No, I didn't copy/paste it from somewhere. You told me to do some practicing with this code to solidify the difference in the variables. So the code I pasted was my practice. It's the same code basically but I changed names and added that useless var intentionally. I was just dissecting each thing, breaking it down, and mapping it so I could understand it better. I wouldn't ever write a real code that way...LOL. But if you deleted that var and changed all the odd-ball things back to match the original code it would be the same as the original code.

The useless var I added so I could change the computers top range guessing number so that I knew which things were controlling what exactly. It was only being left in that code for me to show that I know what it is and does and how if I deleted that var and changed everything back to upper like the original code then everything would have the proper matching top range value. Basically I was doing what you did with changing two of them to be named upperLimit but I took it a step further so I could understand how to control the beast even a little bit more (though useless technically)...LOL.

Yes, I 100% understand that upper in the original code and the oddball things I named those in my code was just a placeholder. But in the original code there is 5 words with the name upper including the var which holds the key value we need for the guessing games top number for the range. I understand that the word upper in the function isn't asking the var upper for the value. It's just a placeholder and the value for that is being sent from elsewhere. But the var upper is the only place that holds the top range value that the function is using so somehow that value from the var upper is being sent to the function. All I was trying to do was find where the value from the var upper was being sent from to the function (which is channeled through the placeholder upper which is just a coincidental naming choice) because it has to be getting sent there somehow. Otherwise there wouldn't be an upper range number being used or controlled like it is.

My code was perhaps an insane funky way to map it but since it was for my own personal notes and exploring I didn't care. I tried to add comments in so you'd understand what I was doing but I guess it wasn't readable like it was in my head which is fine. The point is I think I fully understand the code now. In my mind I have no questions that I have it figured out and it's thanks to all your help, rewatching the videos over and over again, and testing each piece of the code a million ways.

If I'm actually correct might be a different story...LOL. But at least my brain feels it's correct about it at this point which is a step closer then it was when I started the thread...LOL.

I apologize if my comment came off as rude as that was not my intent. I am glad that you are understanding everything better! Happy Coding! :)

Oh no! Not at all, your comment wasn't the slightest bit rude. I didn't take it that way at all and I wasn't giving a sarcastic response. You've been awesome and gone WAY out of your way to help me understand all this. I was just trying to re-explain what I did there because I know it didn't read like i was intending. But at the end let you know that no matter how poorly I'm wording things... I actually think I understand it finally thanks to your help.

I could be wrong in my understanding but I really don't think so now.

Thanks!

You're very welcome, John, and I feel like you do have a much better grasp on the concepts presented here. Honestly, I don't even know ya, but I'm proud of ya! Heck yea! :) Good luck in your future endeavors!

Thanks!