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SVG draw 1 degree arcs in circle using javascript

I have created a SVG circle using Javascript and have to draw 1 degree center line arcs inside circle.
I am struggling with how to calculate the degree and loop through to create the filled arcs as per the image but 1 degree each and fill the circle
Here is what I have done so far
var svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
var svgwidth=550, svgheight=550;
var width = 500, height = 500;
var x = width/2;
var y = width/2;
var r = width/2-10;
svg.setAttribute("width", svgwidth);
svg.setAttribute("height", svgheight);
// create a circle
const circle = document.createElementNS(
"http://www.w3.org/2000/svg",
"circle",
);
circle.setAttributeNS(null, "cx", x);
circle.setAttributeNS(null, "cy", y);
circle.setAttributeNS(null, "r", r);
circle.setAttributeNS(null, 'style', 'fill: none; stroke: blue; stroke-width: 4px;' );
svg.appendChild(circle);
//Arcs
var degree = 1;
var totalArcs = 360;
var middlePointX = width/2;
var middlePointY = width/2;
var newLine = document.createElementNS('http://www.w3.org/2000/svg','line');
newLine.setAttribute('id','line2');
newLine.setAttribute('x1', middlePointX);
newLine.setAttribute('y1',middlePointY);
newLine.setAttribute('x2',100);
newLine.setAttribute('y2',100);
newLine.setAttribute("stroke", "black")
svg.append(newLine);
document.getElementById("div1").appendChild(svg);
<div id="div1">
</div>
https://jsfiddle.net/srnx89h1/9/
Something similar to this but 1 degree fills
Please help

No need for calculations.
Key is to set pathLength=360 on a <circle>, and draw a 1/360 stroke-dashoffset
draw every <circle> at stroke-dashoffset=N to draw N circle segements
define it as a native Web Component <svg-slices> (supported in all modern browsers)
and all you write is HTML:
<svg-slices></svg-slices>
<svg-slices slices="100"></svg-slices>
<svg-slices slices="360"></svg-slices>
<style>
svg-slices {
width: 180px
}
</style>
<svg-slices></svg-slices>
<svg-slices slices="100"></svg-slices>
<svg-slices slices="360"></svg-slices>
<script>
customElements.define("svg-slices", class extends HTMLElement {
connectedCallback() {
this.style.display = "inline-block";
let colors = ["green", "gold","red", "blue", "magenta"];
let length = this.getAttribute("slices") || colors.length;
let slice = ( idx , color = colors.shift() ) => {
colors.push(color); // cycle colors
return `<circle stroke="${color}" stroke-dashoffset="${idx}"
pathLength="${length}" stroke-dasharray="1 ${length-1}"
cx="50%" cy="50%" r="25%" fill="none" stroke-width="50%"/>`;
};
let slices = Array.from({length}, (el, idx) => slice(idx)).join("");
this.innerHTML = `<svg viewBox="0,0,9999,9999">${slices}</svg>`
}
});
</script>
Note how, unlike Libraries, it doesn't matter when <svg-slices> is defined by JS code. Any existing or future added (but not yet processed) <svg-slices> will automagically be Upgraded.
If you are drawing pie-charts, see: https://dev.to/dannyengelman/what-web-technologies-are-required-to-draw-a-pie-chart-in-2021-spoiler-alert-a-standard-web-component-will-do-1j56

Animating SVG polygons

I wrote a code to drawing polygons:
var svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
svg.setAttribute('width', '100%');
svg.setAttribute('height', window.innerHeight);
document.querySelector('#bg').appendChild(svg);
for(var x = 0; x < polygons.length; x++){
var polygon = document.createElementNS(svg.namespaceURI, 'polygon');
polygon.setAttribute('points', polygons[0 + x]);
polygon.setAttribute('fill', polygons[0 + x][1]);
svg.appendChild(polygon);
}
My full code with polygon points:
http://codepen.io/anon/pen/WrqrbB
I would like to animate this polygons similar to this animation:
http://codepen.io/zessx/pen/ZGBMXZ
How to animate my polygons?

You can
call an animation function to manipulate your coordinate values as desired,
convert them to a string, e.g. using .join(),
send the resulting string back to the polygon as its points attribute value, redrawing the shape (as you were already doing when you initially created your shapes), and
have the animation function, when it is finished, call itself again at a reasonable built-in time-delay using requestAnimationFrame.
The following snippet gives a basic idea of what can be done.
(Note that I've redefined the array polygons in my example so that it is different from what you had, but that was done for the sake of simplicity in this example.)
var svg = document.getElementsByTagName("svg")[0];
var polygons = [], numSteps = 100, stepNum = 0;
var coords = [
[40, 20, 80, 20, 80, 60, 40, 60],
[140, 20, 180, 20, 160, 50]
];
for (var x = 0; x < coords.length; x++) {
polygons[x] = document.createElementNS(svg.namespaceURI, 'polygon');
polygons[x].setAttribute('points', coords[x].join());
svg.appendChild(polygons[x]);
}
function anim() {
for (var x = 0; x < coords.length; x++) {
coords[x] = coords[x].map(function(coord) {
return coord + 4 * (Math.random() - 0.5);
});
polygons[x].setAttribute('points', coords[x].join());
stepNum += 1;
}
if (stepNum < numSteps) requestAnimationFrame(anim);
}
anim();
<svg></svg>
UPDATE The above snippet shows generally how to animate a polygon. In your case, however, there is a further issue. On your codepen demo, it is clear that you have hard-coded the point coordinates for each polygon separately. Thus, if you want to move one point, you're going to have to update coordinates in at least 2 if not more places, for every polygon that touches that point.
A better approach would be to create a separate array of all points and then define each polygon with respect to that array. (This is similar to how things are sometimes done in 3D graphics, e.g. WebGL.) The following code snippet demonstrates this approach.
var svg = document.getElementsByTagName("svg")[0];
var polyElems = [], numSteps = 100, stepNum = 0;
var pts = [[120,20], [160,20], [200,20], [240,20], [100,50], [140,50], [180,50], [220,50], [260,50], [120,80], [160,80], [200,80], [240,80]];
var polyPts = [[0,1,5], [1,2,6], [2,3,7], [0,4,5], [1,5,6], [2,6,7], [3,7,8], [4,5,9], [5,6,10], [6,7,11], [7,8,12], [5,9,10], [6,10,11], [7,11,12]];
for (var x = 0; x < polyPts.length; x++) {
polyElems[x] = document.createElementNS(svg.namespaceURI, 'polygon');
polyElems[x].setAttribute('fill', '#'+Math.floor(Math.random()*16777215).toString(16));
// random hex color routine from http://www.paulirish.com/2009/random-hex-color-code-snippets/
drawPolygon(x);
}
function anim() {
pts = pts.map(function(pt) {
return pt.map(function(coord) {
return coord + 3 * (Math.random() - 0.5); // move each point
});
});
for (var x = 0; x < polyPts.length; x++) {drawPolygon(x);}
stepNum += 1;
if (stepNum < numSteps) requestAnimationFrame(anim); // redo anim'n until all anim'n steps done
}
anim(); // start the animation
function drawPolygon(x) {
var ptNums = polyPts[x];
var currCoords = [pts[ptNums[0]], pts[ptNums[1]], pts[ptNums[2]]].join();
// creates a string of coordinates; note that [[1,2],[3,4],[5,6]].join() yields "1,2,3,4,5,6"
polyElems[x].setAttribute('points', currCoords);
svg.appendChild(polyElems[x]);
}
<svg></svg>

How to make javascript canvas draw faster?

I have the following code to display an ECG. I use the canvas to draw the graph background (each grid of 2.5 mm dimension). Later I'm taking the y coordinates from an array array_1 (x coordinates are calculated within the program). The problem with this approach is it will take around 40 seconds to plot the entire graph since there are 1250 values within array array_1. What I could do is I could do the plotting part within a loop in which case, the entire graph is plotted as soon as the page is loaded. But, I need the plotting to happen over the course of 5 seconds. Not more. Not less. How would I alter the code to do this? Please help.
<!DOCTYPE html>
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<canvas id="canvas" width="1350" height="1300" style="background-color: white;"></canvas>
<script type='text/javascript'>
var canvas = document.getElementById("canvas");
var ctxt = canvas.getContext("2d");
var n1 = 1;
var n1_x=49; //Graph x coordinate starting pixel.
var n1_y=72;//Graph y coordinate starting pixel.
var array_1 = []// array from which y coordinates are taken. Has 1250 elements
var ctx = canvas.getContext("2d");
var x=0;
var y=0;
var Line_position=-1;
while(x<=1350)//graph width
{
ctxt.lineWidth = "0.5";
Line_position=Line_position+1;
if(Line_position%5==0)
{
ctxt.lineWidth = "1.5";
}
ctxt.strokeStyle = "black";
ctxt.beginPath();
ctxt.moveTo(x, 0);
ctxt.lineTo(x, 1300);
ctxt.stroke();
x=x+9.43;
}
Line_position=-1;
while(y<=1300)//graph height
{
ctxt.lineWidth = "0.5";
Line_position=Line_position+1;
if(Line_position%5==0)
{
ctxt.lineWidth = "1.5";
}
ctxt.strokeStyle = "black";
ctxt.beginPath();
ctxt.moveTo(0, y);
ctxt.lineTo(1350,y);
ctxt.stroke();
y=y+9.43;
}
drawWave();
function drawWave()
{
requestAnimationFrame(drawWave);
ctx.lineWidth = "1";
ctx.strokeStyle = 'blue';
ctx.beginPath();
ctx.moveTo(n1_x- 1, n1_y+array_1[n1-1]);//move to the pixel position
ctx.lineTo(n1_x, n1_y+array_1[n1]);//Draw to the pixel position
ctx.stroke();
n1_x=n1_x+0.374;//Incrementing pixel so as to traverse x axis.
n1++;
}
</script>
</body>
</html>
Here is the array:
array_1 = [69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,72,72,72,72,72,72,72,73,73,74,74,74,74,74,74,74,73,73,73,73,74,74,74,74,73,73,73,73,73,73,73,73,73,73,73,73,73,74,74,74,73,73,73,72,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,72,71,72,72,72,73,73,73,72,72,72,73,73,73,74,73,73,72,72,72,72,72,73,73,73,73,73,72,72,72,72,73,73,73,72,72,72,71,101,71,70,70,70,69,68,68,67,67,66,66,67,67,69,70,72,72,72,73,73,74,73,73,73,73,73,73,73,73,73,74,76,77,76,70,57,40,22,11,11,22,40,57,69,73,73,71,71,71,72,72,73,73,74,74,74,73,72,72,72,72,72,72,72,72,72,72,72,72,71,71,70,70,71,71,71,71,70,70,69,69,69,69,69,69,69,68,68,68,67,67,66,66,65,65,64,63,63,62,62,62,62,62,62,62,62,63,63,64,65,66,67,68,68,69,70,71,72,72,72,73,73,73,73,72,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,72,73,73,73,73,72,73,73,73,73,73,73,73,73,73,73,72,72,72,72,72,72,73,73,74,74,74,74,74,74,73,73,72,73,73,73,74,73,73,72,72,72,73,73,73,72,72,73,73,74,74,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,71,70,70,70,70,70,69,69,68,67,67,67,67,68,69,71,72,72,73,73,73,73,74,74,74,74,74,73,73,73,73,75,77,78,76,67,53,35,18,8,10,23,41,58,69,73,72,71,70,71,72,73,73,73,73,73,73,73,73,72,72,73,73,73,73,72,71,71,70,70,71,71,71,71,71,71,71,71,70,70,69,69,69,69,68,68,67,67,67,67,67,66,65,65,65,64,63,62,61,61,61,60,60,60,59,60,60,60,61,62,63,65,66,66,67,68,69,70,71,72,72,72,72,73,73,73,72,72,72,72,72,72,72,73,73,73,73,73,73,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,71,71,72,72,73,73,73,72,72,72,72,72,72,73,73,73,73,73,73,73,73,73,72,73,73,73,73,73,73,72,73,73,73,73,73,73,73,72,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,71,71,70,70,69,69,69,68,67,67,66,65,66,66,68,69,70,71,72,72,73,73,73,73,73,73,74,74,74,74,74,74,76,78,78,74,64,48,29,13,5,10,26,45,62,71,73,72,71,71,72,73,73,73,73,73,74,74,74,73,72,72,72,73,73,73,73,73,73,73,72,72,72,72,71,71,71,71,71,71,71,71,71,70,70,69,69,69,69,68,67,66,66,66,66,65,65,64,63,62,62,61,61,60,60,60,60,61,62,62,63,64,65,66,67,68,70,71,72,72,72,72,72,72,73,73,73,73,73,73,73,74,74,75,75,74,74,74,73,73,73,74,73,73,73,73,73,74,74,74,74,74,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,73,73,74,74,74,73,73,73,73,73,73,73,73,73,73,72,72,72,72,73,73,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,73,73,72,72,71,70,70,70,69,69,68,68,67,67,66,67,67,68,69,70,71,72,73,73,74,74,73,73,73,74,75,75,74,73,73,74,76,78,75,67,52,32,15,5,8,22,41,59,69,73,72,71,70,71,72,72,73,73,73,73,73,73,73,73,73,72,72,72,72,72,72,72,72,72,72,71,71,71,70,70,70,70,70,70,70,69,69,69,69,68,68,68,68,67,67,66,65,65,64,64,64,63,62,61,60,60,60,60,60,61,61,62,62,63,64,65,65,66,67,68,69,70,71,71,71,71,71,71,72,72,73,73,73,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,72,72,72,72,72,71,71,71,71,71,71,71,72,72,72,72,72,72,72,72,72,71,71,71,72,72,73,73,72,72,72,72,72,73,73,73,73,73,72,72,72,72,72,73,73,73,73,73,72,72,72,73,73,74,73,73,73,73,73,73,73,73,73,73,73,73,72,72,72,72,71,71,71,70,70,70,70,69,69,68,67,67,68,69,71,72,73,73,73,73,73,73,73,73,74,75,75,75,74,74,74,75,77,77,75,67,52,34,18,10,12,26,45,62,71,74,73,72,72,72,73,74,74,74,75,75,74,74,74,74,74,74,74,74,74,73,73,73,73,74,74,73,73,73,73,73,73,73,72,72,71,71,71,71,71,70,70,70,69,69,69,68,68,68,68,67,66,65,64,63,63,62,62,62,63,63,63,63,64,65,66,67,69,69,70,71,72,72,73,73,74,74,74,74,75,75,76,76,74,72,70,70,69,69 ];

I'd probably go about the task something like this. As mentioned in a comment, we need to draw a number of the data-points per-frame. How many we draw depends on the speed that the browser is able to supply an animation frame.
I've hard-coded the value to 4, since that seems to work on my machine, but with not much more work you can probably make the code time itself and adjust this value on the fly so that your animation runs for as close as possible to the target time. I had a quick go, but the results were awful, I'll leave that as an exercise in research or thought for the reader.
By keeping track of how many frames we've already drawn for the current 'refresh-cycle', we know how far to index into the array for the first point to be drawn for each frame.
I've tried to parameterize the code as much as possible, but it's late and I'm tired, I may have overlooked something somewhere.
<!doctype html>
<html>
<head>
<script>
function byId(id,parent){return (parent == undefined ? document : parent).getElementById(id);}
window.addEventListener('load', onDocLoaded, false);
function onDocLoaded(evt)
{
drawBkg(byId('canvas'), 9.43, 5, "0.5", "1.5", "black");
drawCurFrame();
}
var dataSamples = [69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,69,72,72,72,72,72,72,72,73,73,74,74,74,74,74,74,74,73,73,73,73,74,74,74,74,73,73,73,73,73,73,73,73,73,73,73,73,73,74,74,74,73,73,73,72,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,72,71,72,72,72,73,73,73,72,72,72,73,73,73,74,73,73,72,72,72,72,72,73,73,73,73,73,72,72,72,72,73,73,73,72,72,72,71,101,71,70,70,70,69,68,68,67,67,66,66,67,67,69,70,72,72,72,73,73,74,73,73,73,73,73,73,73,73,73,74,76,77,76,70,57,40,22,11,11,22,40,57,69,73,73,71,71,71,72,72,73,73,74,74,74,73,72,72,72,72,72,72,72,72,72,72,72,72,71,71,70,70,71,71,71,71,70,70,69,69,69,69,69,69,69,68,68,68,67,67,66,66,65,65,64,63,63,62,62,62,62,62,62,62,62,63,63,64,65,66,67,68,68,69,70,71,72,72,72,73,73,73,73,72,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,72,73,73,73,73,72,73,73,73,73,73,73,73,73,73,73,72,72,72,72,72,72,73,73,74,74,74,74,74,74,73,73,72,73,73,73,74,73,73,72,72,72,73,73,73,72,72,73,73,74,74,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,71,70,70,70,70,70,69,69,68,67,67,67,67,68,69,71,72,72,73,73,73,73,74,74,74,74,74,73,73,73,73,75,77,78,76,67,53,35,18,8,10,23,41,58,69,73,72,71,70,71,72,73,73,73,73,73,73,73,73,72,72,73,73,73,73,72,71,71,70,70,71,71,71,71,71,71,71,71,70,70,69,69,69,69,68,68,67,67,67,67,67,66,65,65,65,64,63,62,61,61,61,60,60,60,59,60,60,60,61,62,63,65,66,66,67,68,69,70,71,72,72,72,72,73,73,73,72,72,72,72,72,72,72,73,73,73,73,73,73,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,71,71,72,72,73,73,73,72,72,72,72,72,72,73,73,73,73,73,73,73,73,73,72,73,73,73,73,73,73,72,73,73,73,73,73,73,73,72,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,71,71,70,70,69,69,69,68,67,67,66,65,66,66,68,69,70,71,72,72,73,73,73,73,73,73,74,74,74,74,74,74,76,78,78,74,64,48,29,13,5,10,26,45,62,71,73,72,71,71,72,73,73,73,73,73,74,74,74,73,72,72,72,73,73,73,73,73,73,73,72,72,72,72,71,71,71,71,71,71,71,71,71,70,70,69,69,69,69,68,67,66,66,66,66,65,65,64,63,62,62,61,61,60,60,60,60,61,62,62,63,64,65,66,67,68,70,71,72,72,72,72,72,72,73,73,73,73,73,73,73,74,74,75,75,74,74,74,73,73,73,74,73,73,73,73,73,74,74,74,74,74,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,73,73,74,74,74,73,73,73,73,73,73,73,73,73,73,72,72,72,72,73,73,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,73,73,72,72,71,70,70,70,69,69,68,68,67,67,66,67,67,68,69,70,71,72,73,73,74,74,73,73,73,74,75,75,74,73,73,74,76,78,75,67,52,32,15,5,8,22,41,59,69,73,72,71,70,71,72,72,73,73,73,73,73,73,73,73,73,72,72,72,72,72,72,72,72,72,72,71,71,71,70,70,70,70,70,70,70,69,69,69,69,68,68,68,68,67,67,66,65,65,64,64,64,63,62,61,60,60,60,60,60,61,61,62,62,63,64,65,65,66,67,68,69,70,71,71,71,71,71,71,72,72,73,73,73,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,72,72,72,72,72,72,72,71,71,71,71,71,71,71,72,72,72,72,72,72,72,72,72,71,71,71,72,72,73,73,72,72,72,72,72,73,73,73,73,73,72,72,72,72,72,73,73,73,73,73,72,72,72,73,73,74,73,73,73,73,73,73,73,73,73,73,73,73,72,72,72,72,71,71,71,70,70,70,70,69,69,68,67,67,68,69,71,72,73,73,73,73,73,73,73,73,74,75,75,75,74,74,74,75,77,77,75,67,52,34,18,10,12,26,45,62,71,74,73,72,72,72,73,74,74,74,75,75,74,74,74,74,74,74,74,74,74,73,73,73,73,74,74,73,73,73,73,73,73,73,72,72,71,71,71,71,71,70,70,70,69,69,69,68,68,68,68,67,66,65,64,63,63,62,62,62,63,63,63,63,64,65,66,67,69,69,70,71,72,72,73,73,74,74,74,74,75,75,76,76,74,72,70,70,69,69 ];
function drawBkg(canvasElem, squareSize, numSquaresPerBlock, minorLineWidthStr, majorLineWidthStr, lineColStr)
{
var nLinesDone = 0;
var i, curX, curY;
var ctx = canvasElem.getContext('2d');
ctx.clearRect(0,0,canvasElem.width,canvasElem.height);
// draw the vertical lines
curX=0;
ctx.strokeStyle = lineColStr;
while (curX < canvasElem.width)
{
if (nLinesDone % numSquaresPerBlock == 0)
ctx.lineWidth = majorLineWidthStr;
else
ctx.lineWidth = minorLineWidthStr;
ctx.beginPath();
ctx.moveTo(curX, 0);
ctx.lineTo(curX, canvasElem.height);
ctx.stroke();
curX += squareSize;
nLinesDone++;
}
// draw the horizontal lines
curY=0;
nLinesDone = 0;
while (curY < canvasElem.height)
{
if (nLinesDone % numSquaresPerBlock == 0)
ctx.lineWidth = majorLineWidthStr;
else
ctx.lineWidth = minorLineWidthStr;
ctx.beginPath();
ctx.moveTo(0, curY);
ctx.lineTo(canvasElem.width, curY);
ctx.stroke();
curY += squareSize;
nLinesDone++;
}
}
// position that will be treated as 0,0 when drawing our points.
var originX=49;
var originY=72;
function drawSamples(nSamplesToDraw, firstSample, lineWidthStr, lineColourStr)
{
var can = byId('canvas');
var ctx = can.getContext('2d');
ctx.strokeStyle = lineColourStr;
ctx.lineWidth = lineWidthStr;
console.log(firstSample);
ctx.beginPath();
ctx.moveTo( originX+firstSample-1, dataSamples[firstSample-1]+originY );
for (var i=0; i<nSamplesToDraw; i++)
{
var curSample = dataSamples[i + firstSample];
ctx.lineTo( originX+firstSample+i, curSample+originY );
}
ctx.stroke();
}
var curFrame=0;
var nPointsPerFrame = 4;
function drawCurFrame()
{
if ((dataSamples.length - (nPointsPerFrame * curFrame)) < nPointsPerFrame) // will we over-run the end of the array of datapoints?
{
curFrame = 0; // if so, reset
drawBkg(byId('canvas'), 9.43, 5, "0.5", "1.5", "black");
}
drawSamples(nPointsPerFrame, nPointsPerFrame*curFrame, "1", "blue");
curFrame++;
requestAnimationFrame( drawCurFrame );
}
</script>
<style>
#canvas
{
border: solid 1px black;
background-color: #FFFFFF;
}
</style>
</head>
<body>
<div id='txt'></div>
<canvas id="canvas" width="1350" height="1300"></canvas>
</body>
</html>

Update
Now that I see you have provided some more info I get what you want.
The problem is you need to draw a fixed number of line segments within time t.
As you do not know how long each frame could take you can not rely on a fixed frame rate. The alternative it to just use the current time and save the end time.
Get the start time and then each frame draw all the should be drawn until the current time. As the line segments being drawn will not be displayed until the next screen refresh the time you get will be approx 16ms behind so will need to adjust for that.
What I have done is keep track of the average frame time and used half that time to estimate when the new canvas update will be displayed.
Its a bit pedantic but might as well show how to get a required time as close as possible. If you dont care its a few ms out then just remove the average frame time stuff. You will be at most 30ms off on a slow machine.
var canvas; // canvas
var ctx;
function getCanvas () {
// to do
// get canvas and context
}
function drawGrid () {
// to do
// draw the grid
}
function drawTimedLine(){
if(canvas === undefined){ // if the canvas not available get it
getCanvas();
}
// clear the canvas is repeating animation
ctx.clearRect(0, 0, canvas.width, canvas.height);
drawGrid();
var array_1 = ; // your data
// All stuff needed for timed animation.
// The frame you render will not be displayed untill the next
// vertical refresh which is unknown, Assume it is one frame.
var startDelay = 1000; // if Needed time in milliseconds to delay start
var endTime; // hold the time that the animation has to end
var lastDataPoint; // holds the last point drawn to
var timeToDraw = 5 * 1000; // how long the animation should last
var repeatAfter = 1 *1000; // if you want to repeat the animatoin
var frameCount = 0; // count the frames to get average frame time
var startTime; //the start time;
var numberPoints = array_1.length; // number of points;
var startX = 49; // line starts at
var yOffset = 72; // line Y offset
var endX = 512; // line ends at.
var width = endX - startX; // width
var xStep = width / numberPoints; // X step per point
var pointsPerMS = numberPoints / timeToDraw; // get how many points per ms should be drawn
// function to draw
function drawWave() {
// variable needed
var averageframeTime, timeLeft, i, currentTime;
currentTime = new Date().valueOf(); // gets the time in millisecond;
if (startTime === undefined) { // Is this the first frame
startTime = currentTime; // save the start time;
endTime = currentTime + timeToDraw; // workout when the end time is;
lastDataPoint = 0; // set the data position to the start;
averageframeTime = 0; // no frames counted so frame time is zero
} else {
frameCount += 1; // count the frames
// get the average frame time
averageframeTime = (currentTime - startTime) / frameCount;
}
// get the time this frame
// will most likely be displayed
// then calculate how long
// till the end
timeLeft = endTime - Math.min(endTime, currentTime + averageframeTime / 2);
// now get where we should
// be when the frame is presented
pointPos = Math.floor(pointsPerMS * (timeToDraw - timeLeft));
// now draw the points from where we last left of
// till the new pos;
ctx.lineWidth = 4;
ctx.strokeStyle = 'blue';
ctx.beginPath();
ctx.moveTo( // move to first point
lastDataPoint * xStep + startX,
array_1[lastDataPoint] + yOffset
);
// draw each line from the last drawn to the new position
for (i = lastDataPoint + 1; i <= pointPos && i < numberPoints; i++) {
// Add the line segment
ctx.lineTo(
i * xStep + startX,
array_1[i] + yOffset
);
}
ctx.stroke(); // execute the render commands
lastDataPoint = pointPos; // update the last point
if (pointPos < numberPoints) { // are we there yet???
requestAnimationFrame(drawWave); // no so request another frame
}else{
// if you want to repeat the animation
setTimeout(drawTimedLine , repeatAfter );
}
}
// start the line animation with delay if needed
setTimeout(drawWave,startDelay);
}
// use this if you want it to start as soon as page is ready.
document.addEventListener("DOMContentLoaded",drawTimedLine);
// or use if you want it to start when page has images loaded and is ready
// document.addEventListener("load",drawTimedLine);
I have also added the ability to repeat the animation. If not needed just remove that code
My original answer
Dont know what the problem is with speed as it runs quite well on my machine.
To set up a better start use
function startFunction(){
// your code
}
document.addEventListener("DOMContentLoaded",startFunction);
This will wait until the page has loaded and parsed the page. Images and other media may not have loaded but the page is ready to be manipulated.
Not sure what you mean with 5 seconds. Assuming you may want the thing to sart in 5 seconds.
The following will do that.
document.addEventListener("DOMContentLoaded",function() {setTimeout(startFunction,5000);});
I would ask why plot the graph one entry at a time with requestAnimationFrame 1250 is not that many lines to draw. If you add ctx.beginPath() ctx.moveTo(/*first point*/) then loop all points with ctx.moveTo(/*points*/) then ctx.stroke() will run realtime on but the slowest of devices.
BTW ctx.lineWidth is a Number not a string. Also you have two context? Use the one context for the canvas. Remove ctxt and just use ctx and finally you don't need to add type='text/javascript' to the script tag as Javascript is the default.

1) It cannot take that long to draw 1000 lines, even 100000 lines won't take more than 10 ms on any decent Browser. Look else where the time is lost.
2) The core issue of your code is that it lacks modularity. Split your code into a few clear functions, group the parameters into a few objects only, name and indent things properly.
Below an (incomplete but working) example of how this might look.
var cv, ctx;
var data = null;
var debug = true;
// ---------------------------------------
// define here all graphic related parameters
var gfxParams = {
canvasWidth: 600,
canvasHeight: 600,
gridColor: '#A66',
gridSpacing: 10,
gridLineWidth: 0.5,
gridStrongLinesEvery: 5,
lineColor: '#AEB',
lastLineColor: '#8A9' // , ...
};
// define here all animation related parameters
var animationParams = {
duration: 5,
startTime: -1
}
// ---------------------------------------
// main
// ---------------------------------------
window.onload = function() {
data = getData();
setupCanvas(data);
launchAnimation();
}
// ---------------------------------------
//
function setupCanvas(data) {
cv = document.getElementById('cv');
cv.width = gfxParams.canvasWidth;
cv.height = gfxParams.canvasHeight;
ctx = cv.getContext('2d');
// here you should translate and scale the context
// so that it shows your data.
}
function drawGrid(ctx) {
var i = 0,
pos = 0,
lw = gfxParams.gridLineWidth;
ctx.fillStyle = gfxParams.gridColor;
var vLineCount = gfxParams.canvasWidth / gfxParams.gridSpacing;
for (i = 0; i < vLineCount; i++) {
pos = i * gfxParams.gridSpacing;
ctx.fillRect(pos, 0, lw, gfxParams.canvasHeight);
}
var hLineCount = gfxParams.canvasHeight / gfxParams.gridSpacing;
for (i = 0; i < hLineCount; i++) {
pos = i * gfxParams.gridSpacing;
ctx.fillRect(0, pos, gfxParams.canvasWidth, lw);
}
}
function animate() {
requestAnimationFrame(animate);
var now = Date.now();
// erase screen
ctx.clearRect(0, 0, gfxParams.canvasWidth, gfxParams.canvasHeight);
// draw grid
drawGrid(ctx);
// draw lines
var lastIndex = getLastDrawnIndex(data, now - animationParams.startTime);
drawLines(ctx, data, lastIndex);
if (debug) {
ctx.save();
ctx.fillStyle = '#000';
ctx.fillText(lastIndex + ' lines drawn. Time elapsed : ' + (now - animationParams.startTime), 10, 10);
ctx.restore();
}
}
// comment
function launchAnimation() {
requestAnimationFrame(animate);
animationParams.startTime = Date.now();
}
// comment
function getData() {
var newData = [];
for (var i = 0; i < 500; i++) {
newData.push([Math.random() * 600, Math.random() * 600]);
}
return newData;
}
// comment
function getLastDrawnIndex(data, timeElapsed_ms) {
var timeElapsed = timeElapsed_ms / 1000;
if (timeElapsed >= animationParams.duration) return data.length - 1;
return Math.floor(data.length * timeElapsed / animationParams.duration);
}
function drawLines(ctx, data, lastIndex) {
ctx.strokeStyle = gfxParams.lineColor;
// other ctx setup here.
for (var i = 0; i < lastIndex - 1; i++) {
drawLine(ctx, data[i], data[i + 1]);
}
ctx.strokeStyle = gfxParams.lastLineColor;
drawLine(ctx, data[lastIndex - 1], data[lastIndex]);
}
function drawLine(ctx, p1, p2) {
ctx.beginPath();
ctx.moveTo(p1[0], p1[1]);
ctx.lineTo(p2[0], p2[1]);
ctx.stroke();
}
<canvas id='cv'></canvas>

Using jsDraw2DX, drawn elements do not appear unless an alert is encountered

Using jsDraw2DX, I am trying to use a series on concentric circles to display a position upon a floor plan. An array holds all drawn circles to permit clean removal. The original plan was to have them appear one-by-one, stay for 5 seconds, then to disappear one-by-one. I backed off of that due to troubles with setTimeout, and decided that just the circles image was enough, provided it could stay for a bit, then disappear, ready for the next locate operation. In the stripped down code below, The circles draw OK and remove OK, provided the one alert (marked in the code) is present, but not otherwise.
How might I make this work in the case that no alert was present?
How might I add a 5 second delay before removal?
How might it also work with an additional slight delay between drawing or removing each circle?
CTest
var oldCircle = new Array;
var iter = 0;
var rad = 4;
document.addEventListener("click", printMousePos);
function printMousePos(e) {
var cursorX = e.clientX-10;
var cursorY = e.clientY-10;
//alert("clicked: X: " + cursorX + " Y: " + cursorY);
rad = 4;
animateLocator(cursorX, cursorY);
}
function animateLocator(x, y) {
//alert("Entered animateLocator: rad: "+rad+" x: "+x+" y: "+y);
var start = new Date().getTime();
//alert("starting push");
pushall(rad, x, y);
iter = 0;
//for(i=0; i<10; i++) {
// pushFunc(rad+i*4, x, y);
//}
alert("starting pop"); // This alert box makes it work OK; otherwiudse nothing appears.
setTimeout(popall(), 2000);
}
function pushall(rad, x, y) {
iter = 0;
for(i=0; i<10; i++) {
pushFunc(rad+i*4, x, y);
}
}
function popall() {
iter = 0;
for(i=0; i<10; i++) {
popFunc();
}
}
function pushFunc(rad, x, y) { oldCircle.push(drawCircle(rad, x, y)); }
function popFunc() { oldCircle.pop().remove(); }
function drawCircle(rad, x, y) {
iter++;
//alert("drawCircle rad: "+rad+" x: "+x+" y: "+y);
//Create jxColor object
var col = new jxColor("red");
//Create jxPen object
var pen = new jxPen(col,'2px');
//Create jsGraphics object
var gr = new jxGraphics(document.getElementById("graphics"));
var ctr = new jxPoint(x,y);
var cir = new jxCircle(ctr, rad+iter*4, pen);
//alert("after jxcircle");
cir.draw(gr);
//alert("after draw");
return cir;
}

demo
Remove the alert and Change:
setTimeout(popall(), 2000);
To:
setTimeout(popall, 2000);

Drawing in canvas becomes slower and slower when it draws more stuff during loop

I am trying to incrementally draw 3 lines which are 120 degrees from each other from a point using html5 canvas. The vertex of each lines will become another 3 new center point and spawns another 3 lines at each center and it repeats this..
My problem is, the incremental speed becomes slower and slower (or the drawing becomes slower) as more items are drawn. (maybe something happens in my code but I am not quite familiar how canvas exactly works...). You can copy the code and run it in your local browser to see what I means.
Please see my code (it is very easy to understand) and tell me what causes this.
<!DOCTYPE HTML>
<html>
<head>
<style>
body {
margin: 0px;
padding: 0px;
}
</style>
</head>
<body>
<canvas id="canvas" ></canvas>
<script>
window.requestAnimFrame = (function(callback) {
return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame ||
function(callback) {
window.setTimeout(callback, 1000 / 60);
};
})();
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
canvas.width= window.innerWidth;
canvas.height= window.innerHeight;
// some staring test values
var centerPt={x:canvas.width/2,y:canvas.height/2};
var radius=100;
var angle=0;
// calculate the 3 endpoints at 120 degree separations
var endPt000=anglePoint(centerPt,90);
var endPt120=anglePoint(centerPt,210);
var endPt240=anglePoint(centerPt,330);
var length = 0;
var maxLength = 100;
var centreSet = new Array();
centreSet = getCentres();
var counter = 0;
var end = centreSet.length;
init();
function init() {
start(centreSet[0].x, centreSet[0].y);
}
function start(myX, myY) {
centerPt.x = myX;
centerPt.y = myY;
animate(centerPt, length);
}
function animate(centerPt,length) {
// update
// clear
ctx.clearRect(0, 0, canvas.width, canvas.height);
// draw stuff
draw(centerPt,length);
length = length + 1;
// request new frame
if(length < maxLength){
requestAnimFrame(function() {
animate(centerPt,length);
});
}
else{
if(counter < end){
counter = counter + 1;
centerPt.x = centreSet[counter].x;
centerPt.y = centreSet[counter].y;
endPt000=anglePoint(centerPt,90);
endPt120=anglePoint(centerPt,210);
endPt240=anglePoint(centerPt,330);
length = 0;
setTimeout(function(){animate(centerPt, length);},600);
}
}
}
// draw a red center dot
// draw 3 blue endpoint dots
// draw 3 lines from center going slider% of the way to the endpoints
function draw(centerPt,sliderValue){
var pct=sliderValue;
ctx.clearRect(0,0,canvas.width,canvas.height);
line(centerPt,pointAtPercent(centerPt,endPt000,pct),"green");
line(centerPt,pointAtPercent(centerPt,endPt120,pct),"green");
line(centerPt,pointAtPercent(centerPt,endPt240,pct),"green");
}
// calc XY at the specified angle off the centerpoint
function anglePoint(centerPt,degrees){
var x=centerPt.x-radius*Math.cos( degrees*Math.PI/180 );
var y=centerPt.y-radius*Math.sin( degrees*Math.PI/180 );
return({x:x,y:y});
}
// just draw a line from point1 to point2
function line(pt1,pt2,color){
// ctx.beginPath();
ctx.moveTo(pt1.x,pt1.y);
ctx.lineTo(pt2.x,pt2.y);
ctx.strokeStyle=color;
ctx.lineWidth=2;
ctx.stroke();
}
// calc XY which is a specified percent distance from pt1 to pt2
function pointAtPercent(pt1,pt2,sliderValue) {
// calculate XY at slider% towards pt2
var x = pt1.x + (pt2.x-pt1.x) * sliderValue/100;
var y = pt1.y + (pt2.y-pt1.y) * sliderValue/100;
return({x:x,y:y});
}
//the following are used to get all the center points...
function getCentres() {
var x = window.innerWidth/2;
var y = window.innerHeight/2;
centreSet[0] = centerPt;
var ref = 0;
var end = 0;
var b = true;
var tempCenter = centerPt;
for(var j = 0; j < 5; j++){
tempCenter = centreSet[ref];
end = end + 1;
centreSet[end] = anglePoint(tempCenter,90);
end = end + 1;
centreSet[end] = anglePoint(tempCenter,210);
end = end + 1;
centreSet[end] = anglePoint(tempCenter,330);
ref = ref+1;
}
return centreSet;
}
</script>
</body>
</html>

The problem is you are appending and appending the path. This means that each time you call stroke() the new line together with all the old lines are stroked. You won't see this clearly as the old lines are drawn on top in the same location. And as more and more lines are added the more time it takes to stroke them..
To prevent this you need to break the path. Do this with beginPath().
If you activate your out-commented line it should work fine:
function line(pt1,pt2,color){
ctx.beginPath(); //<-- activate this
ctx.moveTo(pt1.x,pt1.y);
ctx.lineTo(pt2.x,pt2.y);
ctx.strokeStyle=color;
ctx.lineWidth=2;
ctx.stroke();
}