Detect CTRL and SHIFT key without keydown event?

问题:

I've been wondering if I can detect CTRL and SHIFT key being pressed WITHOUT using keydown event.

The reason is that I am creating some sort of Grid Viewer in JavaScript, and I implemented selecting different items by holding CTRL or SHIFT key as it functions in most common viewers, editors and so on.

The problem is that when the focus is not anywhere on the page. For example I'm adding page to the bookmarks. Then I hold CTRL or SHIFT and click on the item, but it acts normally as keydown hasn't been triggered.

Any way of omitting this? Perhaps not, but it can be confusing for customers who will treat it as my own obvious Bug.

回答1:

You don't need any key events at all to detect Shift, Ctrl and Alt when mouse is clicked^MDN.

The Event object contains this information:

element.addEventListener('click', function (e) {
    console.log(e.shiftKey);
    console.log(e.ctrlKey);
    console.log(e.altKey);
});

A demo at jsFiddle.

These properties can be read also in keyboard event handlers.