JavaScript: location.href to open in new window/tab?

I have a JavaScript file from a third party developer. It has a has link which replaces the current page with the target. I want to have this page opened in a new tab.

This is what I have so far:

if (command == 'lightbox') {
 location.href="https://support.wwf.org.uk/earth_hour/index.php?type=individual";
}

Can anyone help me out?

window.open(
  'https://support.wwf.org.uk/earth_hour/index.php?type=individual',
  '_blank' // <- This is what makes it open in a new window.
);

If you want to use location.href to avoid popup problems, you can use an empty <a> ref and then use javascript to click it.

something like in HTML

<a id="anchorID" href="mynewurl" target="_blank"></a>

Then javascript click it as follows

document.getElementById("anchorID").click();