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JavaScript JavaScript Basics (Retired) Working With Numbers The Random Challenge

Shawn Wilson
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.a{fill-rule:evenodd;}techdegree
Shawn Wilson
iOS Development Techdegree Student 7,049 Points
Posted by Shawn Wilson
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Shawn Wilson
iOS Development Techdegree Student 7,049 Points

Curious to know if my solution is considered up to PAR?

just looking for a critique on my code for this project. the Solution works and I know thats what counts here but i learn better with constructive criticism if you wanna look this over and provide some feedback, tips or hints that would be great!

Thanks all, 

/* ********************** */
/* First Random Generator */
/* ********************** */

alert("This number generator will randomly generate a number with the numbers you provide.");
var num1 = prompt("Please select your first number");
var num1 = parseInt(num1);
var random = Math.floor(Math.random() * num1 + 1);
document.write("Your first random number is: " + random + " ");


/* ************************ */
/* Second Random Generator  */
/* ************************ */

var num2 = prompt("Please enter your first number");
var num2 = parseInt(num2);
var num3 = prompt("Please enter your second number");
var num3 = parseInt(num3);
var random2 = Math.ceil(Math.random() * (num2 - num3)) + num1;
document.write("Your second random number is: " + random2);
alert("Thanks for messing around with this little project.");

3 Answers

Marcus Parsons
Marcus Parsons
15,719 Points

Hey Shawn Wilson,

In the first and second number generators, you can be more efficient by combining the parseInt function with the prompt like so:

//Gets the base 10 integer of a prompt
var num1 = parseInt(prompt("Please select your first number"), 10);

In your second number generator, the code just isn't quite right. The point of the 2nd generator is to generate a number that is inclusive of a given range. In order to do that, you have to follow certain mathematical procedures. With your code, the numbers would be all over the place. But, no worries, here is a look at what your code should resemble:

var randMin = parseInt(prompt("Enter a minimum value for your random number:"), 10);
var randMax = parseInt(prompt("Enter a maximum value for your random number:"), 10);
var randNumber = Math.floor(Math.random() * (randMax - randMin + 1)) + randMin;
//For browsers with a Web Console i.e. Firefox or Chrome
console.log("Your random number is: " + randNumber);
//Other browsers
//alert("Your random number is: " + randNumber);

Now when you run that above code, you will always get a number that is within the range provided: [randMin, randMax] inclusive. I hope that helps!

Marcus Parsons
Marcus Parsons
15,719 Points

Anytime, Shawn! Just in case you were wondering about the math involved there:

Let's say we get two numbers in: 50 and 100. That's our minimum and maximum value. If we do the math for randNum you can see that the number will always be within that range, inclusive.

Math.random() has a minimum possible value of 0 and a maximum possible value of 0.9999....

Minimum

So, taking a look at the minimum possible value for randNum, let's plug in the values:

Math.random() rolls to 0.

Math.floor(0 * (100-50+1)) + 50.

0 * anything is 0, so:

0 + 50 = 50

Maximum

And taking a look at the maximum possible value for randNum:

Math.random() rolls to 0.9999...

Math.floor(0.9999... * (100-50+1)) + 50.

Math.floor(0.9999... * 51) + 50.

Math.floor(50.9949) + 50.

50 + 50 = 100

So, now you can see that the range will always be inclusive of whatever the minimum and maximum numbers given. Does that make a little bit more clear, Shawn?

Shawn Wilson
seal-mask
.a{fill-rule:evenodd;}techdegree
Shawn Wilson
iOS Development Techdegree Student 7,049 Points
Shawn Wilson
.a{fill-rule:evenodd;}techdegree
Shawn Wilson
iOS Development Techdegree Student 7,049 Points

it sure dose! as soon as i looked at your code, I saw what you were talking about and it clicked me into the ah-ha moment.

Marcus Parsons
Marcus Parsons
15,719 Points

Awesome! I just like to be very thorough in my explanations haha Good luck, Shawn!

Gina Bégin
PLUS
Gina Bégin
Courses Plus Student 8,613 Points
Gina Bégin
Gina Bégin
Courses Plus Student 8,613 Points

Hey Marcus Parsons — sorry to bring up an older discussion, but I'm on this challenge and having a little trouble. I liked your explanation, so I went to try the code you provided; however, I couldn't get it to go past providing my max number — that was the last alert that showed up. A console didn't pop up and no message showed up on the main web page for me (running Chrome). Was there supposed to be a document.write in the code by chance? Or is my browser just faulty?

Marcus Parsons
Marcus Parsons
15,719 Points

Hi Gina,

If you go into your console, you'll see the command. Notice that I used console.log which logs information out to the console in Chrome and Firefox (and I believe Safari). The console doesn't pop up when you use it; you have to manually bring it up to see things in your console.

You can comment out the line that uses console.log and then uncomment the line for the alert which shows a pop up. I don't like alerts because they can be annoying if used too often. 

var randMin = parseInt(prompt("Enter a minimum value for your random number:"), 10);
var randMax = parseInt(prompt("Enter a maximum value for your random number:"), 10);
var randNumber = Math.floor(Math.random() * (randMax - randMin + 1)) + randMin;
//For browsers with a Web Console i.e. Firefox or Chrome
//console.log("Your random number is: " + randNumber);
//Other browsers
alert("Your random number is: " + randNumber);
Marcus Parsons
Marcus Parsons
15,719 Points

Another problem with using alerts is that when you start writing loops that can go on for an indeterminate amount of time (i.e. a while or do while loop), alert boxes can cause the page to become completely unresponsive because you can't close any tabs while an alert box is being shown. Luckily for us, modern browsers give us the option to stop the page from displaying these boxes after more than one is shown. It can become a giant mess if used improperly.

Marcus Parsons
Marcus Parsons
15,719 Points

And one more thing haha Avoid using document.write except with testing a piece of basic code. document.write is a terrible command to use in applications because it overwrites all of your DOM structure in your page with the first value you pass into it. Every proceeding value passed into it is added to the first one. So, let's say you set up this nice form for people to use with text boxes, a textarea, some select options, etc. and then you use document.write to output some information to the page, it literally overwrites all of that information such that it no longer exists on the page.

If you want to output text to a page, it's best to target an element and use that element'stextContent property or innerHTML when inserting elements, as well.

Okay that's it :)