JavaScript: Check if mouse button down?

Is there a way to detect if a mouse button is currently down in JavaScript?

I know about the "mousedown" event, but that's not what I need. Some time AFTER the mouse button is pressed, I want to be able to detect if it is still pressed down.

Is this possible?

Answers:

Answer

Regarding Pax' solution: it doesn't work if user clicks more than one button intentionally or accidentally. Don't ask me how I know :-(.

The correct code should be like that:

var mouseDown = 0;
document.body.onmousedown = function() { 
  ++mouseDown;
}
document.body.onmouseup = function() {
  --mouseDown;
}

With the test like this:

if(mouseDown){
  // crikey! isn't she a beauty?
}

If you want to know what button is pressed, be prepared to make mouseDown an array of counters and count them separately for separate buttons:

// let's pretend that a mouse doesn't have more than 9 buttons
var mouseDown = [0, 0, 0, 0, 0, 0, 0, 0, 0],
    mouseDownCount = 0;
document.body.onmousedown = function(evt) { 
  ++mouseDown[evt.button];
  ++mouseDownCount;
}
document.body.onmouseup = function(evt) {
  --mouseDown[evt.button];
  --mouseDownCount;
}

Now you can check what buttons were pressed exactly:

if(mouseDownCount){
  // alright, let's lift the little bugger up!
  for(var i = 0; i < mouseDown.length; ++i){
    if(mouseDown[i]){
      // we found it right there!
    }
  }
}

Now be warned that the code above would work only for standard-compliant browsers that pass you a button number starting from 0 and up. IE uses a bit mask of currently pressed buttons:

  • 0 for "nothing is pressed"
  • 1 for left
  • 2 for right
  • 4 for middle
  • and any combination of above, e.g., 5 for left + middle

So adjust your code accordingly! I leave it as an exercise.

And remember: IE uses a global event object called … "event".

Incidentally IE has a feature useful in your case: when other browsers send "button" only for mouse button events (onclick, onmousedown, and onmouseup), IE sends it with onmousemove too. So you can start listening for onmousemove when you need to know the button state, and check for evt.button as soon as you got it — now you know what mouse buttons were pressed:

// for IE only!
document.body.onmousemove = function(){
  if(event.button){
    // aha! we caught a feisty little sheila!
  }
};

Of course you get nothing if she plays dead and not moving.

Relevant links:

Update #1: I don't know why I carried over the document.body-style of code. It will be better to attach event handlers directly to the document.

Answer

the solution isn't good. one could "mousedown" on the document, then "mouseup" outside the browser, and on this case the browser would still be thinking the mouse is down.

the only good solution is using IE.event object.

Answer

The following snippet will attempt to execute the "doStuff" function 2 seconds after the mouseDown event occurs in document.body. If the user lifts up the button, the mouseUp event will occur and cancel the delayed execution.

I'd advise using some method for cross-browser event attachment - setting the mousedown and mouseup properties explicitly was done to simplify the example.

function doStuff() {
  // does something when mouse is down in body for longer than 2 seconds
}

var mousedownTimeout;

document.body.onmousedown = function() { 
  mousedownTimeout = window.setTimeout(doStuff, 2000);
}

document.body.onmouseup = function() {
  window.clearTimeout(mousedownTimeout);
}
Answer

Short and sweet

I'm not sure why none of the previous answers worked for me, but I came up with this solution during a eureka moment. It not only works, but it is also most elegant:

Add to body tag:

onmouseup="down=0;" onmousedown="down=1;"

Then test and execute myfunction() if down equals 1:

onmousemove="if (down==1) myfunction();"
Answer

You can combine @Pax and my answers to also get the duration that the mouse has been down for:

var mousedownTimeout,
    mousedown = 0;

document.body.onmousedown = function() {
  mousedown = 0; 
  window.clearInterval(mousedownTimeout);
  mousedownTimeout = window.setInterval(function() { mousedown += 200 }, 200);
}

document.body.onmouseup = function() {
  mousedown = 0;
  window.clearInterval(mousedownTimeout);
}

Then later:

if (mousedown >= 2000) {
  // do something if the mousebutton has been down for at least 2 seconds
}
Answer

You need to handle the MouseDown and MouseUp and set some flag or something to track it "later down the road"... :(

Answer

If you're working within a complex page with existing mouse event handlers, I'd recommend handling the event on capture (instead of bubble). To do this, just set the 3rd parameter of addEventListener to true.

Additionally, you may want to check for event.which to ensure you're handling actual user interaction and not mouse events, e.g. elem.dispatchEvent(new Event('mousedown')).

var isMouseDown = false;

document.addEventListener('mousedown', function(event) { 
    if ( event.which ) isMouseDown = true;
}, true);

document.addEventListener('mouseup', function(event) { 
    if ( event.which ) isMouseDown = false;
}, true);

Add the handler to document (or window) instead of document.body is important b/c it ensures that mouseup events outside of the window are still recorded.

Answer

Using jQuery, the following solution handles even the "drag off the page then release case".

$(document).mousedown(function(e) {
    mouseDown = true;
}).mouseup(function(e) {
    mouseDown = false;
}).mouseleave(function(e) {
    mouseDown = false;
});

I don't know how it handles multiple mouse buttons. If there were a way to start the click outside the window, then bring the mouse into the window, then this would probably not work properly there either.

Answer

Below jQuery example, when mouse is over $('.element'), color is changing depending on which mouse button is pressed.

var clicableArea = {
    init: function () {
        var self = this;
        ('.element').mouseover(function (e) {
            self.handlemouseClick(e, $(this));
        }).mousedown(function (e) {
            self.handlemouseClick(e, $(this));
        });
    },
    handlemouseClick: function (e, element) {
        if (e.buttons === 1) {//left button
            element.css('background', '#f00');
        }
        if (e.buttons === 2) { //right buttom
            element.css('background', 'none');
        }
    }
};
$(document).ready(function () {
    clicableArea.init();
});
Answer

As said @Jack, when mouseup happens outside of browser window, we are not aware of it...

This code (almost) worked for me:

window.addEventListener('mouseup', mouseUpHandler, false);
window.addEventListener('mousedown', mouseDownHandler, false);

Unfortunately, I won't get the mouseup event in one of those cases:

  • user simultaneously presses a keyboard key and a mouse button, releases mouse button outside of browser window then releases key.
  • user presses two mouse buttons simultaneously, releases one mouse button then the other one, both outside of browser window.
Answer

Well, you can't check if it's down after the event, but you can check if it's Up... If it's up.. it means that no longer is down :P lol

So the user presses the button down (onMouseDown event) ... and after that, you check if is up (onMouseUp). While it's not up, you can do what you need.

Answer

This is an old question, and the answers here seem to mostly advocate for using mousedown and mouseup to keep track of whether a button is pressed. But as others have pointed out, mouseup will only fire when performed within the browser, which can lead to losing track of the button state.

However, MouseEvent (now) indicates which buttons are currently pushed:

  • For all modern browsers (except Safari) use MouseEvent.buttons
  • For Safari, use MouseEvent.which (buttons will be undefined for Safari) Note: which uses different numbers from buttons for Right and Middle clicks.

When registered on document, mousemove will fire immediately as soon as the cursor reenters the browser, so if the user releases outside then the state will be updated as soon as they mouse back inside.

A simple implementation might look like:

var leftMouseButtonOnlyDown = false;

function setLeftButtonState(e) {
  leftMouseButtonOnlyDown = e.buttons === undefined 
    ? e.which === 1 
    : e.buttons === 1;
}

document.body.onmousedown = setLeftButtonState;
document.body.onmousemove = setLeftButtonState;
document.body.onmouseup = setLeftButtonState;

If more complicated scenarios are required (different buttons/multiple buttons/control keys), check out the MouseEvent docs. When/if Safari lifts its game, this should get easier.

Answer

I think the best approach to this is to keep your own record of the mouse button state, as follows:

var mouseDown = 0;
document.body.onmousedown = function() { 
    mouseDown = 1;
}
document.body.onmouseup = function() {
    mouseDown = 0;
}

and then, later in your code:

if (mouseDown == 1) {
    // the mouse is down, do what you have to do.
}
Answer

I know this is an old post, but I thought the tracking of mouse button using mouse up/down felt a bit clunky, so I found an alternative that may appeal to some.

<style>
    div.myDiv:active {
        cursor: default;
    }
</style>

<script>
    function handleMove( div ) {
        var style = getComputedStyle( div );
        if (style.getPropertyValue('cursor') == 'default')
        {
            // You're down and moving here!
        }
    }
</script>

<div class='myDiv' onmousemove='handleMove(this);'>Click and drag me!</div>

The :active selector handles the mouse click much better than mouse up/down, you just need a way of reading that state in the onmousemove event. For that I needed to cheat and relied on the fact that the default cursor is "auto" and I just change it to "default", which is what auto selects by default.

You can use anything in the object that is returned by getComputedStyle that you can use as a flag without upsetting the look of your page e.g. border-color.

I would have liked to set my own user defined style in the :active section, but I couldn't get that to work. It would be better if it's possible.

Answer

Using the MouseEvent api, to check the pressed button, if any:

document.addEventListener('mousedown', (e) => console.log(e.buttons))

Return:

A number representing one or more buttons. For more than one button pressed simultaneously, the values are combined (e.g., 3 is primary + secondary).

0 : No button or un-initialized
1 : Primary button (usually the left button)
2 : Secondary button (usually the right button)
4 : Auxilary button (usually the mouse wheel button or middle button)
8 : 4th button (typically the "Browser Back" button)
16 : 5th button (typically the "Browser Forward" button)
Answer
        var mousedown = 0;
        $(function(){
            document.onmousedown = function(e){
                mousedown = mousedown | getWindowStyleButton(e);
                e = e || window.event;
                console.log("Button: " + e.button + " Which: " + e.which + " MouseDown: " + mousedown);
            }

            document.onmouseup = function(e){
                mousedown = mousedown ^ getWindowStyleButton(e);
                e = e || window.event;
                console.log("Button: " + e.button + " Which: " + e.which + " MouseDown: " + mousedown);
            }

            document.oncontextmenu = function(e){
                // to suppress oncontextmenu because it blocks
                // a mouseup when two buttons are pressed and 
                // the right-mouse button is released before
                // the other button.
                return false;
            }
        });

        function getWindowStyleButton(e){
            var button = 0;
                if (e) {
                    if (e.button === 0) button = 1;
                    else if (e.button === 1) button = 4;
                    else if (e.button === 2) button = 2;  
                }else if (window.event){
                    button = window.event.button;
                }
            return button;
        }

this cross-browser version works fine for me.

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