Open a URL in a new tab (and not a new window)

This is a trick,
function openInNewTab(url) {
window.open(url, ‘_blank’).focus();
}

//or just
window.open(url, ‘_blank’).focus();

In most cases, this should happen directly in the onclick handler for the link to prevent pop-up blockers, and the default “new window” behavior. You could do it this way, or by adding an event listener to your DOM object.

Open a URL in a new tab using JavaScript

Nothing an author can do can choose to open in a new tab instead of a new window; it is a user preference. (Note that the default user preference in most browsers is for new tabs, so a trivial test on a browser where that preference hasn’t been changed will not demonstrate this.)
CSS3 proposed target-new, but the specification was abandoned.
The reverse is not true; by specifying certain window features for the window in the third argument of window.open(), you can trigger a new window when the preference is for tabs.