threejs vector3d to screen projection

vector3d to screen projection.js

function toScreenXY( object, camera, div ) {
	var mat = object.matrixWorld;
	var pos = new THREE.Vector3();
	pos = mat.multiplyVector3(pos);
        projected = pos.clone();
        projScreenMat = new THREE.Matrix4();
        projScreenMat.multiply( camera.projectionMatrix, camera.matrixWorldInverse );
        projScreenMat.multiplyVector3( projected );

        var offset = findOffset(div);

        return { x: ( projected.x + 1 ) * div.width / 2 + offset.left,
             y: ( - projected.y + 1) * div.height / 2 + offset.top };
    }

function findOffset(element) { 
      var pos = new Object();
      pos.left = pos.top = 0;        
      if (element.offsetParent)  
      { 
        do  
        { 
          pos.left += element.offsetLeft; 
          pos.top += element.offsetTop; 
        } while (element = element.offsetParent); 
      } 
      return pos;
    }