HTML 5 canvas：检测，如果在将鼠标移到 canvas 上时按下鼠标按钮

Question

I was trying to detect, if mouse is pressed while moving over CANVAS:

canvas.addEventListener('mousemove', function (evt) {
           ...
        });

Setting a flag inside mousedown and skipping it in mouseup is a bad idea, because user can release mouse button outside the canvas.

Answer 1

evt.which will be 1 if left mouse button is held down during the fired mousemove event, 0 if it's not.

Test with:

document.addEventListener("mousemove", function (e) {
    console.log(e.which);
});