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JavaScript

Posted by Bob Allan
Bob Allan
10,900 Points

Strange random results ... what am I missing?

I'm stumped! What am I doing wrong? The results a strange numbers above the upper input number. Thanks in advance for your help.

function randomBetweenNumbers( upper, lower ) { return Math.floor(Math.random() * (upper - lower +1)) + lower; }

var foo = prompt("What is the upper number?"); var bar = prompt("What is the lower number?"); document.write( randomBetweenNumbers( foo , bar ) );

2 Answers

tobiastrinkler
.a{fill-rule:evenodd;}techdegree
tobiastrinkler
Full Stack JavaScript Techdegree Student 16,538 Points

Hi Bob,

You are almost there you just have to use the parseInt() method to convert the string to a number. 

function randomBetweenNumbers( lower, upper ) { 
  return Math.floor(Math.random() * (upper - lower +1)) + lower; }

var foo = parseInt(prompt("What is the upper number?"));
var bar = parseInt(prompt("What is the lower number?"));

document.write( randomBetweenNumbers(foo,bar) );
Bob Allan
Bob Allan
10,900 Points

Oh my gosh, that never crossed my mind! YES! Thank you so much Tobias!

Shay Paustovsky
Shay Paustovsky
969 Points
Shay Paustovsky
Shay Paustovsky
969 Points

Hi there,

It generates above the input number because the 'lower' paramater is outside the statement that generates the random number.

It should look like this: 

function getRandomNum(upper, lower) {
  return Math.floor(Math.random() * (upper - lower) + lower)
}

Let me explain : So first the statement generates a random number with the given difference from the function's arguments, then it adds the 'lower' paramater argument ( think of it like the 1), and then rounds up the difference because Math.random() returns a floating-point/decimal random number value.

Hopefully I've helped

Shay

Bob Allan
Bob Allan
10,900 Points

In my frustration I forgot to explain exactly what I wanted the code to accomplish (looking for a random number between two numbers). I do see exactly what you are saying, but it was not the issue. Thanks for attempting to help Shay, I do appreciate it.