asking user input with prompt to provide the numbers

Question

I did the code challenge like Dave showed in the video by putting the random numbers in the code when calling the function and it worked as it should. As a practice I thought to rewrite it a bit so that a user would provide the numbers. Theoretically it works BUT the maths doesn't add up properly.

For example, I write 1 for the small number and 10 for the large number and get 91. But if I delete the promt and write the numbers below in the document.write(getRandom()); it works as it should displaying numbers between 1 and 10.

function getRandom(lower, upper) {
    var lower = prompt("Please enter a small number.");
    var upper = prompt("Please enter a large number.");
    return Math.floor(Math.random() * (upper - lower + 1)) + lower;
}
document.write(getRandom());

I validated both options are no errors come up. Am I missing something?

Answer 1 · 2016-08-14T08:28:09Z

August 14, 2016 8:28am

Because the prompt returns strings. When you sum strings the result will be different

For example '3' + '1' = '31' instead of 3 + 1 = 4

To fix this, you need to parse the prompts:

var lower = parseInt(prompt("Please enter a small number."));
var upper = parseInt(prompt("Please enter a large number."));

Also - there is no need to pass in lower and upper arguments when you declare them inside you function anyway.

Full code:

function getRandom() {
    var lower = parseInt(prompt("Please enter a small number."));
    var upper = parseInt(prompt("Please enter a large number."));

    return Math.floor(Math.random() * (upper - lower + 1)) + lower;
}
document.write(getRandom());

Answer 2 · 2016-08-18T03:42:34Z

August 18, 2016 3:42am

Thanks, makes sense now. Forgot about the parseInt.

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Liga Zarina

Liga Zarina

asking user input with prompt to provide the numbers

2 Answers

Thomas Nilsen

Thomas Nilsen

Liga Zarina

Liga Zarina