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JavaScript JavaScript Numbers The Math Object Random Number Challenge – Two Numbers Solution

Stephen Cole
PLUS
Stephen Cole
Courses Plus Student 15,809 Points

My solution allows for negative numbers.

It doesn't seem to matter if the inputs are low/high or high/low. To allow for negative numbers, I added a test for the input to be >= 0 or <=0.

I chose to output the results to the HTML.

Also, I put the prompt inside parseInt to save a conversion step. I'm not lazy, I'm efficient. It looks similar but is, in fact, different. (No matter what my parents say.)*

// Access the DOM
const main = document.querySelector('main');

// Collect input from a user

const userInputLow = parseInt( prompt("Provide the low number:") ); 
const userInputHigh = parseInt( prompt("Provide the high number:") );

// If the low number is 0, it will test as false
// Added two conditions with a logical or to prevent this

if ( ( userInputLow <= 0 || userInputLow >= 0 ) && userInputHigh ) { 

  const randomNumber = Math.floor( Math.random() * ( userInputHigh - userInputLow + 1)) + userInputLow;

  // Create a message displaying the random number

  main.innerHTML = `
    <h2>${randomNumber} is a random number between ${userInputLow} and ${userInputHigh}</h2>
    `;
} else {
    // userInput tested as false/NaN

    main.innerHTML = 
    `<h2>Required inputs are numbers.  Refresh the page and try again.</h2>`;

}

2 Answers

Steven Parker
Steven Parker
229,005 Points

What if the low number was negative and the high number was 0?   :see_no_evil:

Steven Parker
Steven Parker
229,005 Points

OK, one more suggestion. Instead of testing ranges that cover every possible number, check for not a non-number:

// so instead of this:
if ( ( userInputLow <= 0 || userInputLow >= 0 ) && ( userInputHigh <= 0 || userInputHigh >=0 ) ) {
// try this:
if ( !isNaN(userInputLow) && !isNaN(userInputHigh) ) {
Stephen Cole
PLUS
Stephen Cole
Courses Plus Student 15,809 Points

Ooo... good catch!

Fixed:

// Access the DOM
const main = document.querySelector('main');

// Collect input from a user

const userInputLow = parseInt( prompt("Provide the low number:") ); 
const userInputHigh = parseInt( prompt("Provide the high number:") );

// If the low number is 0, it will test as false
// Added two conditions with a logical or to prevent this

if ( ( userInputLow <= 0 || userInputLow >= 0 ) && ( userInputHigh <= 0 || userInputHight >=0 ) ) { 

  const randomNumber = Math.floor( Math.random() * ( userInputHigh - userInputLow + 1)) + userInputLow;

  // Create a message displaying the random number

  main.innerHTML = `
    <h2>${randomNumber} is a random number between ${userInputLow} and ${userInputHigh}</h2>
    `;
} else {
    // userInput tested as false/NaN

    main.innerHTML = 
    `<h2>Required inputs are numbers.  Refresh the page and try again.</h2>`;

}