Why am I getting undefined output Javascript?

Question

I keep getting undefined before my output text in JS. Here is my code.

<!DOCTYPE html>
<html>
<head>
    <link rel="stylesheet" type="text/css" href="css/style.css">
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Learning javascript</title>
</head>
<body>

    <p id="arrayString"></p>



    <!-- Javascript -->
    <script type="text/javascript" src="JS/app2.js"></script>
</body>
</html>

This is my JS

var arrayString;
var myArray=["Ms.Vickies", "Old Dutch", "Lays"];
for (var i=0; i<myArray.length; i++) {
    arrayString=arrayString+myArray[i];
}
document.getElementById("arrayString").innerHTML=arrayString;

my output is undefinedMs.VickiesOld DutchLays

In addition why no spaces? I am new to JS but am working my way up. Cannot figure this out.

To allow people to easily help you, consider making a jsfiddle of your problem. jsfiddle is a site where you can run javascript with html live in the browser. — Relequestual
– Relequestual, Commented Jan 7, 2015 at 14:04

Mike · Accepted Answer · 2015-01-07 13:59:55Z

7

It's because in your first loop iteration, arrayString is undefined. Set it equal to an empty string instead.

Instead of declaring arrayString like so:

var arrayString;

Initialize it with an empty string:

var arrayString = '';

answered Jan 7, 2015 at 13:59

Mike

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Comments

Latheesan · Accepted Answer · 2015-01-07 14:02:10Z

1

Because you are initiating a null/undefined variable by doing this: var arrayString;

You can fix it by doing this: var arrayString = "";

Better yet, instead of using a for loop, you can do it like this:

var myArray=["Ms.Vickies", "Old Dutch", "Lays"];
document.getElementById("arrayString").innerHTML = myArray.join(" ");

More info: http://www.w3schools.com/jsref/jsref_join.asp

answered Jan 7, 2015 at 14:02

Latheesan

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Comments

getty_advaanz · Accepted Answer · 2015-01-07 14:06:03Z

0

In code ,you have just declared,not initialized.so,just replace

  var arrayString;

with

 var arrayString = '';

Hope it helps...Thank you.

answered Jan 7, 2015 at 14:06

getty_advaanz

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