score:33

Accepted answer

You should be able to use something like this:

d3.select(window).on("click", function() {
    if (d3.event.shiftKey) {
        alert("Mouse+Shift pressed");
    }
});

Demo: http://jsfiddle.net/SO_AMK/NTGKG/1/

score:2

Maybe it is necessary to use:

if (d3.event.sourceEvent.shiftKey) {
  console.log("shift pressed");
}

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