My snapping works in Firefox only, any legal code?

I'm learning JS (think I'm not too old to learn) and coding app for drawing electronics at: http://3lectronics.com/draw/Atarado-Draw1.html

The most powerful help I can get is here, because of many great guys sharing knowledge. I stacked cause of 20x20px snapping to grid because I found some hacky (obviously) way to make those snapping. It is working only with Firefox and Seamonkey...code:

function ev_canvas (ev) {
if (ev.layerX || ev.layerX == 0) { // Firefox
  x2 = (ev.layerX /2).toFixed(-1) *2 ;
  y2 = (ev.layerY /2).toFixed(-1) *2 ;
} else if (ev.offsetX || ev.offsetX == 0) { // Opera
  x2 = ev.offsetX;
  y2 = e开发者_开发问答v.offsetY;
}

It works excellent (you can try), but other browsers disobey to run it. I found that Chrome doesn't like negative value in .toFixed(), and without this it works, but I don't have snapping... Any idea....Thanx.

toFixed is only supported between 0 and 20 in Chrome

Another way to round to the 10's place would be to divide by 10, round, and than multiply by 10.

var x2 = Math.round(ev.layerX /20) *20 ;

Not sure what is up with the *2 /2 you have going on, but I left it in there.