onMouseMove get mouse position

Question

In javascript, within the javascript event hander for onMouseMove how do I get the mouse position in x, y corrdinates relative to the top of the page?

Answer 1

if you can use jQuery, then this will help:

<div id="divA" style="width:100px;height:100px;clear:both;"></div>
<span></span><span></span>
<script>
    $("#divA").mousemove(function(e){
      var pageCoords = "( " + e.pageX + ", " + e.pageY + " )";
      var clientCoords = "( " + e.clientX + ", " + e.clientY + " )";
      $("span:first").text("( e.pageX, e.pageY ) - " + pageCoords);
      $("span:last").text("( e.clientX, e.clientY ) - " + clientCoords);
    });

</script>

here is pure javascript only example:

var tempX = 0;
  var tempY = 0;

  function getMouseXY(e) {
    if (IE) { // grab the x-y pos.s if browser is IE
      tempX = event.clientX + document.body.scrollLeft;
      tempY = event.clientY + document.body.scrollTop;
    }
    else {  // grab the x-y pos.s if browser is NS
      tempX = e.pageX;
      tempY = e.pageY;
    }  

    if (tempX < 0){tempX = 0;}
    if (tempY < 0){tempY = 0;}  

    document.Show.MouseX.value = tempX;//MouseX is textbox
    document.Show.MouseY.value = tempY;//MouseY is textbox

    return true;
  }

Answer 2

This is tried and works in all browsers:

   function getMousePos(e) {
       return {x:e.clientX,y:e.clientY};
   }

Now you can use it in an event like this:

  document.onmousemove=function(e) {
       var mousecoords = getMousePos(e);
       alert(mousecoords.x);alert(mousecoords.y);
  };

Answer 3

Especially with mousemove events, that fire fast and furious, its good to pare down the handlers before you use them-

var whereAt= (function(){
    if(window.pageXOffset!= undefined){
        return function(ev){
            return [ev.clientX+window.pageXOffset,
            ev.clientY+window.pageYOffset];
        }
    }
    else return function(){
        var ev= window.event,
        d= document.documentElement, b= document.body;
        return [ev.clientX+d.scrollLeft+ b.scrollLeft,
        ev.clientY+d.scrollTop+ b.scrollTop];
    }
})()

document.ondblclick=function(e){alert(whereAt(e))};

Answer 4

It might be a bit overkill to use d3.js just for finding mouse coordinates, but they have a very useful function called d3.mouse(*container*). Below is an example of doing what you want to do:

var coordinates = [0,0];
d3.select('html') // Selects the 'html' element
  .on('mousemove', function()
    {
      coordinates = d3.mouse(this); // Gets the mouse coordinates with respect to
                                    // the top of the page (because I selected
                                    // 'html')
    });

In the above case, the x-coordinate would be coordinates[0], and the y-coordinate would be coordinates[1]. This is extremely handy, because you can get the mouse coordinates with respect to any container you want to by exchanging 'html' with the tag (e.g. 'body'), class name (e.g. '.class_name'), or id (e.g. '#element_id').