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JavaScript JavaScript Basics (Retired) Creating Reusable Code with Functions Random Number Challenge

Saqib Ishfaq
Saqib Ishfaq
13,912 Points
Posted by Saqib Ishfaq
Saqib Ishfaq
13,912 Points

Any suggestions abt my code?

function getRandomNum(upperNum, lowerNum) {

  var randomNumGen = Math.floor(Math.random() * (upperNum - lowerNum + 1)) + 1; 
  return randomNumGen;
}

console.log ( getRandomNum(78, 9) );
console.log ( getRandomNum(100, 1) );
console.log ( getRandomNum(6, 1) );
console.log ( getRandomNum(6, 0) );

9 Answers

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

Assuming the formula is intended to generate random numbers between the upperNum and lowerNum (inclusively), then the last term should be lowerNum instead of 1.

Optionally, you could eliminate the randomNumGen variable and return the result of calculation directly.

It's probably more conventional to have the lower number argument come first, but it's not an issue as long as it's used consistently (which it is in your sample calls).

And some "best practice" style guides would suggest removing the blank line inside the function, and having the open parenthesis follow a function or method name with no space in between.

Saqib Ishfaq
Saqib Ishfaq
13,912 Points
Saqib Ishfaq
Saqib Ishfaq
13,912 Points

sorry i dint undertand the 1st part of ur answer.

Math.floor(Math.random() * (upperNum - lowerNum + lowerNum)) + lowerNum

is that wot u meant? and how would removing randomNumGen be any option, i dont understand! and lastly ,why does my code

console.log ( getRandomNum(6, 0) );
``
generated 7 number its not between "0" and "6"
???
Gaurav Yadav
Gaurav Yadav
5,047 Points
Gaurav Yadav
Gaurav Yadav
5,047 Points

Why are you using upperNum and lowerNum... I mean your code is perfectly fine..but u could just use one value? In other words if u have to explain what does ur function do...what would you say?

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

I suspect this code is intended to generate a random number within a specified range, which it will do once the error is corrected.

Saqib Ishfaq
Saqib Ishfaq
13,912 Points
Saqib Ishfaq
Saqib Ishfaq
13,912 Points

i thought our purpose of this challenge was to generate a number between two values...thats why i did this:(

Gaurav Yadav
Gaurav Yadav
5,047 Points
Gaurav Yadav
Gaurav Yadav
5,047 Points

But for that there is no need of lowerNum don't u think? For example in the first console.log the program gives a random number between 0 and 70 both included ...so there was no need of 78 or 9...he could have just provided an upperNum argument of 70 and modified some of his code...But again may be he wanted to do something else...

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

But based on the provided arguments, I would expect that what is required is a random number between 78 and 9 (not 70 and 0).

Gaurav Yadav
Gaurav Yadav
5,047 Points
Gaurav Yadav
Gaurav Yadav
5,047 Points 
var randomNumGen = Math.floor(Math.random() * (upperNum - lowerNum + 1)) + 1;

Suppose upperNum = 78 and lowerNum = 9, the term (upperNum - lowerNum + 1) becomes 70. Math.random() * 70 will give a number between 0 and 70, 70 not included, then Math.floor() will give an integer value between 0 and 70, 70 not included, then the program adds 1 and returns the number, So according to me the program gives a value between 0 and 70, both included..Please explain if I am wrong

Saqib Ishfaq
Saqib Ishfaq
13,912 Points
Saqib Ishfaq
Saqib Ishfaq
13,912 Points

yes steven thats what my intention was! is it wrong?

Saqib Ishfaq
Saqib Ishfaq
13,912 Points
Saqib Ishfaq
Saqib Ishfaq
13,912 Points

Gaurav does it mean when i put "78" and "9" it actually getting a value between "0" and "70" instead?

Gaurav Yadav
Gaurav Yadav
5,047 Points
Gaurav Yadav
Gaurav Yadav
5,047 Points

yes, run the code with 78 and 9 and you will see that you will never get a number greater than 70, then try to understand why is it happening, meanwhile I am trying to get the solution of your original problem, u want a random number in the range of upperNum and lowerNum, right?

Saqib Ishfaq
Saqib Ishfaq
13,912 Points
Saqib Ishfaq
Saqib Ishfaq
13,912 Points

yes. that's wot my intention was as per challenge. and i just saw the solution video ,teacher did the same thing passing two arguments , with one change he put lower 1st and then upper. does it make any difference? like in the formula provided if we put lower 1st or upper?

Gaurav Yadav
Gaurav Yadav
5,047 Points
Gaurav Yadav
Gaurav Yadav
5,047 Points

no, it does not make any difference which argument you pass first, but you have to be careful that howsoever you are passing the values, your function declaration should accept parameters in that order. for example if you are passing 

getRandomNum(6,0)

you function declaration should be: 

function getRandomNum(upperNum, lowerNum){
//your code
}

and not : 

function getRandomNum(lowerNum, upperNum){
//your code
}
Gaurav Yadav
Gaurav Yadav
5,047 Points
Gaurav Yadav
Gaurav Yadav
5,047 Points

Did u understand what is the problem with the current version of your code? Why is it returning a number between 0 and 70?

Saqib Ishfaq
Saqib Ishfaq
13,912 Points
Saqib Ishfaq
Saqib Ishfaq
13,912 Points

kind of, coz its adding the "1" in the end.. ...after i saw the solution video ,i have to add lowerNum instead of "1" . dont know why though?

Gaurav Yadav
Gaurav Yadav
5,047 Points
Gaurav Yadav
Gaurav Yadav
5,047 Points

yes, Do this:

  1. read what does Math.random() function do on Mozilla Developer Network (MDN).
  2. Understand what does your version of code do ie. why does your code logs out a number between 0 and 70.
  3. Try to understand what happens when you add lowerNum instead of 1. Don't lose hope..If you still dont understand, leave a comment, i will try to explain further. But, try to do it yourself first
Saqib Ishfaq
Saqib Ishfaq
13,912 Points
Saqib Ishfaq
Saqib Ishfaq
13,912 Points

yeh just read the whole article on it on MDN, make sense now! i was just doing simple maths in my head, n doing same on the code but its the formula in action, which explains on MDN .

Saqib Ishfaq
Saqib Ishfaq
13,912 Points
Saqib Ishfaq
Saqib Ishfaq
13,912 Points

Don't see the best answer option on the answer I wanna mark as best

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

Take another look, every answer should have a "best answer" option.

Chris Phua
Chris Phua
6,884 Points
Chris Phua
Chris Phua
6,884 Points 
var upperValue = prompt("Please key in an upper value");
var lowerValue = prompt("Please key in an lower value");

function randNumGenerator(x, y){
  var randNum = Math.floor(Math.random() * parseInt(x));
    if (randNum >= parseInt(y) && randNum <= parseInt(x)) {
        return randNum;
    } else {
      return randNumGenerator(x, y); /*---> RECURSIVE: call the same function again until it falls into the statement*/
    }
}
console.log(randNumGenerator(upperValue, lowerValue));

/*This method of calling is not efficient but it solves the challenge. Hope it helps.*/