在没有Jquery的情况下在Canvas上进行鼠标坐标

Question

I am currently using:

e.pageX - $("#canvas").offset().left

This is the only thing I am using Jquery for, so I would prefer to re-write this using just javascript.

What can I use to replace this?

Answer 1

The answer provided by N Rohler works well only in Internet Explorer (with some bugs prior to IE8 - but I guess it won't be a problem for you since you're using a canvas and pageX), and in Opera if the padding is 0, and in Safari/Chrome if the border width is 0 too. In Firefox, unfortunately, offsetX and offsetY are undefined. http://www.quirksmode.org/dom/w3c_cssom.html#mousepos

Kaninepete, I think you should reconsider, for the sake of simplicity, the way of getting the mouse coordinates relatively to your canvas element. All you have to do is to calculate the position of the canvas, which is a pretty simple task using .getBoundingClientRect() (also, don't forget to add scroll offsets if necessary), and subtract it from pageX and pageY.

Answer 2

var x = e.offsetX,
    y = e.offsetY;

Updated (again) for (correct) Firefox compatibility:

var rect = e.target.getBoundingClientRect();
var x = e.offsetX || e.pageX - rect.left - window.scrollX,
    y = e.offsetY || e.pageY - rect.top - window.scrollY;

Answer 3

You can replace it by the below code

<canvas onmouseDown="mouseDown(event)" width="500" height="500"></canvas>


function mouseDown(e)
{
  var x=e.clientX-canvas.offsetLeft;
  var y=e.clientY-canvas.offsetTop; 
}