Get random string from array list

Question

I have the code as below, but can't get it work. It should return 1 value from the myArray, but it returns "undefined". What's the problem?

HTML

<div id="quote"></div>

JavaScript

var myArray = ['January', 'February', 'March'];
var rand = myArray[Math.floor(Math.random() * myArray.length)];

function showquote(){
    document.getElementById('quote').innerHTML = myArray[rand];
}
showquote();

JSFiddle can be found here.

So, rand is already equal to month name. document.getElementById('quote').innerHTML = rand; — Andy Jones
– Andy Jones, Commented Jul 4, 2014 at 8:22
and although this is simple error... have an upvote for clearly written question with a fiddle too — Andy Jones
– Andy Jones, Commented Jul 4, 2014 at 8:25
@AndyJones I've submitted a close vote on the basis that the error is so simple and the answers unlikely to help anyone else in future. — Alnitak
– Alnitak, Commented Jul 4, 2014 at 8:27

Yaje · Accepted Answer · 2014-07-04 08:38:17Z

4

this fiddle works.

var myArray = ['January', 'February', 'March'];
var rand = Math.floor(Math.random() * myArray.length);

function showquote(){
    document.getElementById('quote').innerHTML = myArray[rand];
}
showquote();

the problem is with this line

var rand = myArray[Math.floor(Math.random() * myArray.length)]; // dereferenced myArray[] twice here

edited Jul 4, 2014 at 8:38

answered Jul 4, 2014 at 8:23

Yaje

2,82920 silver badges33 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Alnitak Over a year ago

@ejay_francisco the error is not a syntax error. It's merely a case of the OP accidentally trying to dereference myArray[] twice - once in the rand call and again in showquote().

wilsont · Accepted Answer · 2014-07-16 07:20:34Z

3

The problem is that rand' is already the value from the array (e.g. "January"), var rand = myArray[Math.floor(Math.random() * myArray.length)];

so you cannot get value from the array again using myArray['January'].

You should change your Js function as below

function showquote(){
    document.getElementById('quote').innerHTML = rand;
}

Or change your variable

var rand = Math.floor(Math.random() * myArray.length);

edited Jul 16, 2014 at 7:20

answered Jul 4, 2014 at 8:25

wilsont

1416 bronze badges

1 Comment

Alnitak Over a year ago

@DNac this is the clearest answer here, the only one to correctly explain the double indexing into the array. IMHO you should accept this one.

Falydoor · Accepted Answer · 2014-07-04 08:22:37Z

2

var rand = Math.floor(Math.random() * myArray.length);

answered Jul 4, 2014 at 8:22

Falydoor

4626 silver badges21 bronze badges

Comments

sukhi · Accepted Answer · 2014-07-04 08:34:23Z

2

use this

var myArray = ['January', 'February', 'March'];

var rand = Math.floor(Math.random() * myArray.length);

function showquote(){

    document.getElementById('quote').innerHTML = myArray[rand];
}
showquote();

answered Jul 4, 2014 at 8:34

sukhi

9247 silver badges11 bronze badges

Collectives™ on Stack Overflow

Get random string from array list

4 Answers 4

1 Comment

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related