My class testPage.php looks like this:

<?php
class testPage extends Page {

private static $db = array(

'Location1' => 'Text',
'Location2' => 'Text',
'Location3' => 'Text'

);

public function getCMSFields() {

$fields = parent::getCMSFields();
$fields->addFieldToTab('Root.Content.Locations', TextField::create('Location1','Location #1'));
$fields->addFieldToTab('Root.Content.Locations', TextField::create('Location2','Location #2'));
$fields->addFieldToTab('Root.Content.Locations', TextField::create('Location3','Location #3'));

return $fields;

}

}

And my template (testPage.ss) looks like this:

<ul>

<script type="text/javascript">

for ( i=1; i<4; i++ ) {

document.write('<li>$Location [ i ]</li>');

}

</script>

</ul>

I've used the CMS to add values to each location e.g. Location #1 = Ipswich. But the template doesn't return any location values. I expected it to return Ipswich as the first line item for example. But it just returns " [ i ] " as each line item. Obviously I'm doing something simple wrong. Can anyone advise please?

Have you completed the lessons, John?
This is pretty basic template stuff... "for" loops do not exist, it's more like...

<% loop $MyLocations %>
      <!-- do stuff -->
<% end_loop %>

See here... https://www.silverstripe.org/learn/lessons/adding-dynamic-content

What would I loop through in this case? loop $db doesn't work