Getting 'Undefined' when searching through array of quotes - Javascript

Question

I am working on a random quote generator, where I first randomly generate a number between 0 and the length of the array 'quotes,' then return that quote.

function getQuote() {
 var quotes = ["I never met a toby that I didn't like ~ Kimya Dawson", "Blood in my beard ~ Aesop Rock", "How many roads must a man walk down? ~ Bob Dylan", "Orange is the new black ~ Jenji Kohan"];

function randomNumber(min, max) {
 var quote = Math.floor(Math.random() * (max - min +1)) + min
 return quotes[quote]; 
}; 
return randomNumber(0, quotes.length);
};
getQuote();

It works most of the time, but every so often it will return 'Undefined.' I did not have this problem when testing with an array of single words like 'hello,' 'green,' etc., it only happens when I add spaces.

Tobias · Accepted Answer · 2015-08-26 18:12:37Z

2

Math.floor(Math.random() * (max - min +1)) + min

can return max which points to a non-existing array element. Array indices go from 0 to length - 1.

It should be

Math.floor(Math.random() * (max - min)) + min

answered Aug 26, 2015 at 18:12

Tobias

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Pointy · Accepted Answer · 2015-08-26 18:12:13Z

1

That +1 in the code that finds a random index is your problem.

There are 4 quotes, so max is 4. 4-0+1 is 5, not 4, so you're going to generate the value 4 every once in a while, and there is nothing at that position in the array. (The quotes are at indexes 0, 1, 2, and 3.)

answered Aug 26, 2015 at 18:12

Pointy

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Comments

mmarkowski · Accepted Answer · 2015-08-26 18:18:18Z

0

Arrays starts from 0, so in your case max is 3 (quotes[3]). However length function returns number of elements (4).

return randomNumber(0, quotes.length-1);

answered Aug 26, 2015 at 18:18

mmarkowski

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