function(len) {
	    var s = (len || 1) / this.magnitude();
	    this.x = s * this.x;
	    this.y = s * this.y;
	    return this;
        }
function(len) {
	    var s = (len || 1) / this.magnitude();
	    this.x = s * this.x;
	    this.y = s * this.y;
	    return this;
        }
function ( len ) { var s = ( len || 1 ) / this . magnitude ( ) ; this . x = s * this . x ; this . y = s * this . y ; return this ; }
Scale the line segment between (0,0) and me to have a length of len.
Scale the line segment between ( 0 0 ) and me to have a length of len .