SVG Bezier Curve thru points

HTML

<body>
acknowledgement <a href="https://www.particleincell.com/2012/bezier-splines/"> https://www.particleincell.com/2012/bezier-splines/</a><br/>




<svg  xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" height=400 width=800 onload="init();">
<script>
<![CDATA[
/* bezier-spline.js
 *
 * computes cubic bezier coefficients to generate a smooth
 * line through specified points. couples with SVG graphics 
 * for interactive processing.
 *
 * For more info see:
 * http://www.particleincell.com/2012/bezier-splines/ 
 *
 * Lubos Brieda, Particle In Cell Consulting LLC, 2012
 * you may freely use this algorithm in your codes however where feasible
 * please include a link/reference to the source article
 */ 

var svg=document.getElementsByTagName('svg')[0]; /*svg object*/
var S=new Array() /*splines*/
var V=new Array() /*vertices*/
var C 	/*current object*/
var x0,y0	/*svg offset*/

/*saves elements as global variables*/
function init()
{
	/*create splines*/
	S[0] = createPath("blue");
	S[1] = createPath("red");
	S[2] = createPath("green");
	S[3] = createPath("brown");

	/*create control points, one more than splines*/
	V[0] = createKnot(60,60);
	V[1] = createKnot(220,300);
	V[2] = createKnot(420,300);
	V[3] = createKnot(700,240);
	V[4] = createKnot(600,150);
	
	updateSplines();
}
/*creates and adds an SVG circle to represent knots*/
function createKnot(x,y)
{
	var C=document.createElementNS("http://www.w3.org/2000/svg","circle")
	C.setAttributeNS(null,"r",22)
	C.setAttributeNS(null,"cx",x)
	C.setAttributeNS(null,"cy",y)
	C.setAttributeNS(null,"fill","gold")
	C.setAttributeNS(null,"stroke","black")
	C.setAttributeNS(null,"stroke-width","2")
	C.setAttributeNS(null,"onmousedown","startMove(evt)")
	svg.appendChild(C)	
	return C
}

/*creates and adds an SVG path without defining the nodes*/
function createPath(color,width)
{		
	width = (typeof width == 'undefined' ? "8" : width);
	var...