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JavaScript JavaScript Numbers The Math Object Random Number Challenge – Solution

Nelson Jimenez
Nelson Jimenez
3,475 Points
Posted by Nelson Jimenez
Nelson Jimenez
3,475 Points

what is wrong with my code? 

// Collect input from a user
const maxNumber = parseInt(prompt("Enter a maximum number"));
const minNumber = parseInt(prompt("Enter a minimum number"));

// Convert the input to a number

// Use Math.random() and the user's number to generate a random number
if (maxNumber) {
  const rollDice = Math.round(Math.random() * maxNumber) + minNumber;
  const message = `${rollDice} is a number between ${minNumber} and ${maxNumber}`;
  document.write(message);
} else {
  document.write("You need to enter a number. try again.");
}


// Create a message displaying the random number

1 Answer

Rohald van Merode
seal-mask
STAFF
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Rohald van Merode
Treehouse Staff
Rohald van Merode
.a{fill-rule:evenodd;}techdegree
Rohald van Merode
Treehouse Staff

Hey Nelson Jimenez 👋

Looks like the logic for the rollDice variable is a bit off. Currently you're multiplying the random number with the maxNumber and then add the minNumber to the rounded outcome of that. Let's break down what could happen if a user would set the max to be 100 and the min to be 50: 

const rollDice = Math.round(Math.random() * 100) + 50;

Math.random() will return a random number from 0 up to but not including 1. For this example let's see what would happen if Math.random returns the number 0.9871:

const rollDice = Math.round(0.9871 * 100) + 50;
// 0.9871 * 100 = 98.71
// Math.round(98.71) = 99
// 99 + 50 = 149

This would result in a 149 dice roll which is outside of the 50-100 bounds set by the user 🙂

Guil goes over a possible solution in the next video if you're interested.

I hope this clears things up and helps you to get going again 😃

Nelson Jimenez
Nelson Jimenez
3,475 Points
Nelson Jimenez
Nelson Jimenez
3,475 Points

thank you for your detailed answer