window.open with middle mouse click

I'm using the code below to open a link using both the left and the middle mouse buttons. As it is now, if press the middle button, a new tab opens, and then you have to manually click that tab to see its content. I'd like to point out this only happens in FireFox.

In Chrome however, the new tab is opened and then also brought into focus right after you middle-click.

Is there a quick way to make the script work the same way in FireFox as it does in Chrome?

Thank you,
Alex

CODE...

window.open with middle mouse click

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