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Can't figure out how to fix this: "Uncaught TypeError (webcam.snap is not a function)" <-- javascript

I have a JavaScript script that I am getting an error for that I can't figure out. I am trying to take a picture of the webcam feed using JavaScript
The error is:
Uncaught TypeError: webcam.snap is not a function
I am using webcam.js to take the snapshot.
Here is my JavaScript code:
<script>
var video = document.createElement("video");
var canvasElement = document.getElementById("canvas");
var canvas = canvasElement.getContext("2d");
var loadingMessage = document.getElementById("loadingMessage");
var outputContainer = document.getElementById("output");
var outputMessage = document.getElementById("outputMessage");
var outputData = document.getElementById("outputData");
const jsQR = require("jsqr");
function drawLine(begin, end, color) {
canvas.beginPath();
canvas.moveTo(begin.x, begin.y);
canvas.lineTo(end.x, end.y);
canvas.lineWidth = 4;
canvas.strokeStyle = color;
canvas.stroke();
}
// Use facingMode: environment to attemt to get the front camera on phones
navigator.mediaDevices.getUserMedia({ video: { facingMode: "environment" } }).then(function(stream) {
video.srcObject = stream;
video.setAttribute("playsinline", true); // required to tell iOS safari we don't want fullscreen
video.play();
requestAnimationFrame(tick);
});
function tick() {
loadingMessage.innerText = "⌛ Loading video..."
if (video.readyState === video.HAVE_ENOUGH_DATA) {
loadingMessage.hidden = true;
canvasElement.hidden = false;
outputContainer.hidden = false;
canvasElement.height = video.videoHeight;
canvasElement.width = video.videoWidth;
canvas.drawImage(video, 0, 0, canvasElement.width, canvasElement.height);
var imageData = canvas.getImageData(0, 0, canvasElement.width, canvasElement.height);
var code = jsQR(imageData.data, imageData.width, imageData.height, {
inversionAttempts: "invertFirst",
});
if (code) {
drawLine(code.location.topLeftCorner, code.location.topRightCorner, "#FF3B58");
drawLine(code.location.topRightCorner, code.location.bottomRightCorner, "#FF3B58");
drawLine(code.location.bottomRightCorner, code.location.bottomLeftCorner, "#FF3B58");
drawLine(code.location.bottomLeftCorner, code.location.topLeftCorner, "#FF3B58");
outputMessage.hidden = true;
outputData.parentElement.hidden = false;
outputData.innerText = code.data;
takeSnapShot();
}
else {
outputMessage.hidden = false;
outputData.parentElement.hidden = true;
}
}
requestAnimationFrame(tick);
}
// TAKE A SNAPSHOT.
takeSnapShot = function () {
webcam.snap(function (data_uri) {
downloadImage('video', data_uri);
});
}
// DOWNLOAD THE IMAGE.
downloadImage = function (name, datauri) {
var a = document.createElement('a');
a.setAttribute('download', name + '.png');
a.setAttribute('href', datauri);
a.click();
}
</script>
This is the first line that causes a problem:
webcam.snap(function (data_uri) {
downloadImage('video', data_uri);
});
This is the second line that causes a problem:
takeSnapShot();
how do I correct this properly?
****** UPDATE ******
The version of webcam.js I am using is WebcamJS v1.0.26. My application is a Django application that launches the HTML file as defined in main.js.
snap: function(user_callback, user_canvas) {
// use global callback and canvas if not defined as parameter
if (!user_callback) user_callback = this.params.user_callback;
if (!user_canvas) user_canvas = this.params.user_canvas;
// take snapshot and return image data uri
var self = this;
var params = this.params;
if (!this.loaded) return this.dispatch('error', new WebcamError("Webcam is not loaded yet"));
// if (!this.live) return this.dispatch('error', new WebcamError("Webcam is not live yet"));
if (!user_callback) return this.dispatch('error', new WebcamError("Please provide a callback function or canvas to snap()"));
// if we have an active preview freeze, use that
if (this.preview_active) {
this.savePreview( user_callback, user_canvas );
return null;
}
// create offscreen canvas element to hold pixels
var canvas = document.createElement('canvas');
canvas.width = this.params.dest_width;
canvas.height = this.params.dest_height;
var context = canvas.getContext('2d');
// flip canvas horizontally if desired
if (this.params.flip_horiz) {
context.translate( params.dest_width, 0 );
context.scale( -1, 1 );
}
// create inline function, called after image load (flash) or immediately (native)
var func = function() {
// render image if needed (flash)
if (this.src && this.width && this.height) {
context.drawImage(this, 0, 0, params.dest_width, params.dest_height);
}
// crop if desired
if (params.crop_width && params.crop_height) {
var crop_canvas = document.createElement('canvas');
crop_canvas.width = params.crop_width;
crop_canvas.height = params.crop_height;
var crop_context = crop_canvas.getContext('2d');
crop_context.drawImage( canvas,
Math.floor( (params.dest_width / 2) - (params.crop_width / 2) ),
Math.floor( (params.dest_height / 2) - (params.crop_height / 2) ),
params.crop_width,
params.crop_height,
0,
0,
params.crop_width,
params.crop_height
);
// swap canvases
context = crop_context;
canvas = crop_canvas;
}
// render to user canvas if desired
if (user_canvas) {
var user_context = user_canvas.getContext('2d');
user_context.drawImage( canvas, 0, 0 );
}
// fire user callback if desired
user_callback(
user_canvas ? null : canvas.toDataURL('image/' + params.image_format, params.jpeg_quality / 100 ),
canvas,
context
);
};
// grab image frame from userMedia or flash movie
if (this.userMedia) {
// native implementation
context.drawImage(this.video, 0, 0, this.params.dest_width, this.params.dest_height);
// fire callback right away
func();
}
else if (this.iOS) {
var div = document.getElementById(this.container.id+'-ios_div');
var img = document.getElementById(this.container.id+'-ios_img');
var input = document.getElementById(this.container.id+'-ios_input');
// function for handle snapshot event (call user_callback and reset the interface)
iFunc = function(event) {
func.call(img);
img.removeEventListener('load', iFunc);
div.style.backgroundImage = 'none';
img.removeAttribute('src');
input.value = null;
};
if (!input.value) {
// No image selected yet, activate input field
img.addEventListener('load', iFunc);
input.style.display = 'block';
input.focus();
input.click();
input.style.display = 'none';
} else {
// Image already selected
iFunc(null);
}
}
else {
// flash fallback
var raw_data = this.getMovie()._snap();
// render to image, fire callback when complete
var img = new Image();
img.onload = func;
img.src = 'data:image/'+this.params.image_format+';base64,' + raw_data;
}
return null;
},

Your implementation doesn't need Webcamjs, because you're using navigator media devices.
You can either use WebcamJS by initializing it at first and attaching it to some canvas, like in the following code
Webcam.set({
width: 320,
height: 240,
image_format: 'jpeg',
jpeg_quality: 90
});
Webcam.attach( '#my_camera' );
Or you can update your takeSnapShot function to the following :
takeSnapShot = function () {
downloadImage('video',canvasElement.toDataURL())
// Webcam.snap(function (data_uri) {
// downloadImage('video', data_uri);
// });
}
Here's a working example based on your code https://codepen.io/majdsalloum/pen/RwVKBbK

It seems like either:
the webcam's code are missing (not imported)
in this case you need to first call the script from the URL and add it with script tag
<script src="WEBCAM_JS_SOURCE">
or
they are imported, but used with typo. From the webcam source code it is defined as:
var Webcam = {
version: '1.0.26',
// globals
...
};
so you should use with a capital one.

Javascript canvas "game". Hero mooves only one time

Im trying to make simple game in canvas. I made animation for hero using setTimeout() function. I check pressed keys with function moove(e):
Everything works pretty fine when i press leftarrow or rightarrow for the first time, but then hero doesnt moove. Any recomendations to the code is appreciated.
var cns = document.getElementById("can");
cns.height = 600;
cns.width = 300;
var ctx = cns.getContext("2d");
var hero = new Image();
hero.src = "images/hero.png";
hero.onload = function() {
ctx.drawImage(hero, 120, 570);
hero.xx = 120;
hero.yy = 570;
};
var intervalL, intervalR, intervalLL, intervalRR;
var keys = [];
function moove(e) {
keys[e.keyCode] = (e.type == "keydown");
if (keys[37]) {
clearTimeout(intervalR);
clearTimeout(intervalRR);
goLeft(hero);
} else {
clearTimeout(intervalL);
clearTimeout(intervalLL);
}
if (keys[39]) {
clearTimeout(intervalL);
clearTimeout(intervalLL);
goRight(hero);
} else {
clearTimeout(intervalR);
clearTimeout(intervalRR);
}
}
function goLeft(img) {
var x = img.xx,
y = img.yy;
function f() {
ctx.clearRect(img.xx, img.yy, img.width, img.height);
ctx.drawImage(img, x, y);
img.xx = x;
img.yy = y;
x -= 1.2;
if (x < -35) {
x = cns.width;
}
}
if (!intervalL) {
intervalL = setTimeout(function run() {
f();
intervalLL = setTimeout(run, 5);
}, 5);
}
}
Function goRight is similiar to goLeft.
Function moove is called in tag body onkeydown='moove(event)' onkeyup='moove(event)'.
You can check the project here: https://github.com/Fabulotus/Fabu/tree/master/Canvas%20game%20-%20dodge%20and%20jump

The reason it doesn't work the first time is because the first time through you are setting the position to its previous position (x = image.xx) then updating x after you draw. You should update the x value x -= 1.2 before calling drawImage

Here is a "working" version of your code:
var cns = document.getElementById("can");
cns.height = 170;
cns.width = 600;
var ctx = cns.getContext("2d");
var hero = new Image();
hero.src = "http://swagger-net-test.azurewebsites.net/api/Image";
hero.onload = function() {
ctx.drawImage(hero, cns.width-10, cns.height/2);
hero.xx = cns.width-10;
hero.yy = cns.height/2;
};
var intervalL, intervalR, intervalLL, intervalRR;
var keys = [];
function goLeft(img) {
function f() {
ctx.beginPath()
ctx.clearRect(0, 0, cns.width, cns.height);
ctx.drawImage(img, img.xx, img.yy);
img.xx--;
if (img.xx < -img.width) {
img.xx = cns.width;
}
}
if (!intervalL) {
intervalL = setTimeout(function run() {
f();
intervalLL = setTimeout(run, 5);
}, 5);
}
}
goLeft(hero)
<canvas id="can">
As you can see the function goLeft has been significantly simplified.
One recommendation: avoid the many setTimeout and clearTimeout instead use one setInterval to call a draw function that takes care of drawing everything on your game, all the other function should just update the position of your gameObjects.

Javascript Key Pressed + setTimeout()

I am making a game with html and javascript. Just for clarification, this is not a duplicate or anything. Nothing has the answer I need. Also before I explain, I want to say I have no trouble with the key listener, my game knows when a key is pressed and when it is released. Okay, I have 5 frames of a character walking. I have a while loop that basically says while the key D is pressed or Right arrow is pressed, then increment the frames to make it look like the character is walking. Then it has a setTimeout function that pauses for 1/10 of a second. This should make it look like the character is walking. I know it has something to do with the setTimeout() function. Here is the while loop:
while (keys[68] || keys[39]) {
charFrame++;
setTimeout(function() {
}, 100);
}
Then here is my code:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Sparring Spartans</title>
<style type="text/css">
</style>
</head>
<body>
<canvas id="canvas" width="1000" height="600"></canvas>
<script type="text/javascript">
var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d");
var width = canvas.width;
var height = canvas.height;
var groundX = 0, groundY = 400;
var playerx = width/2, playery = groundY-120;
var charFrame = 1;
var speed = 4;
var keys = [];
window.addEventListener("keydown", function(e) {
keys[e.keyCode] = true;
}, false);
window.addEventListener("keyup", function(e) {
delete keys[e.keyCode];
}, false);
var spartan1 = new Image();
spartan1.src = "spartan1.png";
var spartan2 = new Image();
spartan2.src = "spartan2.png";
var spartan3 = new Image();
spartan3.src = "spartan3.png";
var spartan4 = new Image();
spartan4.src = "spartan4.png";
var spartan5 = new Image();
spartan5.src = "spartan5.png";
var stone = new Image();
stone.src = "stone.png";
function game() {
update();
render();
}
function player() {
if (charFrame === 1) {
context.drawImage(spartan1, playerx, playery);
} else if (charFrame === 2) {
context.drawImage(spartan2, playerx, playery);
} else if (charFrame === 3) {
context.drawImage(spartan3, playerx, playery);
} else if (charFrame === 4) {
context.drawImage(spartan4, playerx, playery);
} else if (charFrame === 5) {
context.drawImage(spartan5, playerx, playery);
}
}
function ground() {
for (var i = 0; i <= 1000; i += 55) {
context.drawImage(stone, i, groundY);
}
for (var i = 0; i <= 1000; i += 55) {
context.drawImage(stone, i, groundY+55);
}
for (var i = 0; i <= 1000; i += 55) {
context.drawImage(stone, i, groundY+110);
}
for (var i = 0; i <= 1000; i += 55) {
context.drawImage(stone, i, groundY+165);
}
}
function manager() {
ground();
while (keys[68] || keys[39]) {
charFrame++;
setTimeout(function() {
}, 100);
}
player();
}
function update() {
manager();
player();
}
function render() {
context.fillStyle = "#AFE4FF";
context.fillRect(0, 0, width, height);
manager();
}
setInterval(function() {
game();
}, 1000/30);
</script>
</body>
</html>
What am I doing wrong? I know it HAS to be the setTimeout, but I have tried to fix this problem many times. The images don't even change.

Because your manager function gets called 30 times per second, you should check your keypress once per frame using an if statement instead of a loop:
function manager() {
ground();
if (keys[68] || keys[39]) {
charFrame++;
}
}
In addition, your manager function is getting called twice per frame, once in the update function and once in the render function. Also, your player function is called both in update and in manager, again twice per frame. Your code will need some refactoring in order to work properly, to make sure nothing gets called twice per frame.

reload canvas createjs/easeljs animation with ajax load causes layering or display issue

I have a canvas animation that has been created with createjs. The entire animation script including init() function is loaded via jquery: $.getScript() on page load.
The init() and handlecomplete() function included below is then run which attaches the animation to a html canvas element on the page.
var canvas, stage, exportRoot, audio;
var tweens = [];
function init() {
canvas = document.getElementById("canvas");
images = images||{};
if (stage) {
stage.enableDOMEvents(false);
stage.removeAllChildren();
createjs.Ticker.removeAllEventListeners()
stage.enableDOMEvents(true);
}
if (audio ) {
audio.stop();
}
removeTweens();
exportRoot = null;
audio = null;
stage = null;
var loader = new createjs.LoadQueue(false);
loader.installPlugin(createjs.Sound);
loader.addEventListener("fileload", handleFileLoad);
loader.addEventListener("complete", handleComplete);
loader.loadManifest(lib.properties.manifest);
}
function handleComplete() {
exportRoot = new lib.animation2();
stage = new createjs.Stage(canvas);
stage.addChild(exportRoot);
stage.update();
stage.canvas.width = 1280;
stage.canvas.height = 720;
resizeToFit();
stage.update();
createjs.Ticker.setFPS(lib.properties.fps);
createjs.Ticker.addEventListener("tick", stage);
createjs.Ticker.addEventListener("tick", updateTimer);
if (lib.properties.audiovolume) {
audio = createjs.Sound.play("audio", createjs.Sound.INTERRUPT_EARLY, 0, 0, -1, lib.properties.audiovolume);
}
exportRoot.gotoAndPlay(startFrame );
}
My issue is when the user makes a change, we load the script a second time using the same jquery method which returns the updated script. The init() function then executes properly and the new animation plays correctly, but our animated text (using the animateText below) does not appear on the canvas. This function is also loaded dynamically with other functions.
Checking the tween arrays, they are being created and removed as required, but they are not visible.
They are either layered behind the new animation, or not being attached to the new canvas or something else?
Simply refreshing the page will then load the new script and text properly. So clearly something in the dynamic loading of the script?
var animateText = function(localString, startX, startY, letterClip, endObject, font, color) {
var waitAmount = 0;
var offSetAmount = 20;
for(var i = 0; i < localString.length; i++){
var fl_MyInstance = new letterClip();
fl_MyInstance.localName.text = localString[i];
if(font != null){
fl_MyInstance.localName.font = font;
}
if(color != null){
fl_MyInstance.localName.color = color;
}
var localX = startX;
var localY = startY;
fl_MyInstance.x = startX + offSetAmount;
var beginX = startX + offSetAmount
offSetAmount = offSetAmount - 4
fl_MyInstance.y = startY;
fl_MyInstance.alpha = 0;
fl_MyInstance.scaleX = 0.1;
fl_MyInstance.scaleY = 0.1;
var bounds = fl_MyInstance.getBounds();
startX += bounds.width + 0;
var target = fl_MyInstance;
var tween = createjs.Tween.get(target, {
loop: false
}).wait(waitAmount)
.to({
x: localX,
y: localY,
alpha: 1,
scaleX: 1,
scaleY: 1
}, 400, createjs.Ease.circOut);
tween.waitAmount = waitAmount;
if(endObject == null){
tween.endObject = {
x: localX,
y: localY,
alpha: 0,
scaleX: 0.1,
scaleY: 0.1
}
} else {
tween.endObject = {
x: localX - endObject.x,
y: localY - endObject.y,
alpha: endObject.alpha,
scaleX: endObject.scaleX,
scaleY: endObject.scaleY
}
}
tween.targetClip = fl_MyInstance;
tween.arrayIndex = tweens.length;
tweens.push(tween);
waitAmount += 20;
stage.addChild(fl_MyInstance);
}
}
var removeTweens = function(){
for(var i = 0; i<tweens.length; i++){
if(tweens[i] != null){
var tween = tweens[i];
stage.removeChild(tween.targetClip);
tweens[tween.arrayIndex] = null;
}
}
}
var closeTweens = function(){
for(var i = 0; i<tweens.length; i++){
if(tweens[i] != null){
var tween = tweens[i];
createjs.Tween.get(tween.targetClip, {
loop: false
}).wait(tween.waitAmount).to(tween.endObject, 400, createjs.Ease.circOut).call(function(){
stage.removeChild(tween.targetClip);
tweens[tween.arrayIndex] = null;
});
}
}
}
var finalTweens = function(){
for(var i = 0; i<tweens.length; i++){
if(tweens[i] != null){
var tween = tweens[i];
createjs.Tween.get(tween.targetClip, {
loop: false
}).to(tween.endObject, 400, createjs.Ease.circOut);
}
}
}
Since the rest of the animation works perfectly using this method of dynamic loading, I don't think it is something in the loading. But there must be something missing in animateText and reloading functions that causes the issue.

Canvas and animation

I was trying to create a sample paint application using HTML 5 canvas. Then I added a button to redraw what user had drawn earlier. I am not sure what I am doing wrong or may be completely wrong. When I click redraw button multiple times it generates some magical animation by drawing lines all over. Even though if I log the starting point of drawing the image its same every time.
Demo: http://jsfiddle.net/BW57H/6/
Steps to reproduce:
Draw some circle or rectangle or something by clicking the mouse and dragging it on the rectangular box. Then click reset and redraw , click redraw couple of times after that and see the result.
I am not sure what I have done. I have not read a lot about Canvas. But I am curious to know what is going on here. Thanks.
html
<body>
<canvas id="paint" width="600px" height="300px"></canvas>
<div id="controls">
<button name="reset" id="reset">Reset</button>
<button name="redraw" id="redraw">Re-Draw</button>
</div>
</body>
css
#paint{
border: solid;
}
js
$(document).ready(function(){
var x, y, context, painter;
var xCounter = 0 , yCounter = 0;
var xarray = [];
var yarray = [];
function init(){
while(document.getElementById("paint") === undefined){
//do nothing
}
console.log("Loaded document now registering events for canvas");
var canvas = document.getElementById("paint");
context = canvas.getContext('2d');
painter = new Painter();
canvas.addEventListener('mousedown', capture, false);
canvas.addEventListener('mouseup', capture, false);
canvas.addEventListener('mousemove', capture, false);
document.getElementById("reset").addEventListener("click",function(){ clearCanvas(canvas);}, false);
document.getElementById("redraw").addEventListener("click", function(){
autoDraw();
}, false);
}
function clearCanvas(canvas){
context.save();
// Use the identity matrix while clearing the canvas
context.setTransform(1, 0, 0, 1, 0, 0);
context.clearRect(0, 0, canvas.width, canvas.height);
// Restore the transform
context.restore();
};
function capture(event){
if(event.which !== 1){
return;
}
x = event.layerX;
y = event.layerY;
switch(event.type){
case 'mousedown':
painter.startPaint(event);
break;
case 'mouseup':
painter.endPaint(event);
break;
case 'mousemove':
painter.paint(event);
break;
}
};
var Painter = function(){
var self = this;
self.paintStarted = false;
self.startPaint = function(event){
self.resetRecordingParams();
self.paintStarted = true;
context.beginPath();
context.moveTo(x,y);
self.record();
}
self.endPaint = function(event){
self.paintStarted = false;
self.record();
self.paint(event)
}
self.paint = function(event){
if(self.paintStarted){
context.lineTo(x,y);
context.stroke();
self.record();
}
}
self.record = function(){
xarray[xCounter++] = x;
yarray[yCounter++] = y;
}
self.resetRecordingParams = function(){
xarray = [];
yarray = [];
xCounter = 0;
yCounter= 0;
}
return self;
}
function autoDraw(){
context.beginPath();
console.log('starting at: '+xarray[0]+','+yarray[0]);
context.moveTo(xarray[0],yarray[0]);
for (var i = 0; i < xarray.length; i++) {
setTimeout(drawLineSlowly, 1000+(i*20), i);
};
}
function drawLineSlowly(i)
{
context.lineTo(xarray[i],yarray[i]);
context.stroke();
}
init();
});

You don't have any kind of check to see whether or not you are already drawing, so here is your code with those changes commented, as well as the real-pixel-location fixes (http://jsfiddle.net/upgradellc/htJXy/1/):
$(document).ready(function(){
var x, y, context, painter, canvas;
var xCounter = 0 , yCounter = 0;
var xarray = [];
var yarray = [];
function init(){
while(document.getElementById("paint") === undefined){
//do nothing
}
console.log("Loaded document now registering events for canvas");
canvas = document.getElementById("paint");
context = canvas.getContext('2d');
painter = new Painter();
canvas.addEventListener('mousedown', capture, false);
canvas.addEventListener('mouseup', capture, false);
canvas.addEventListener('mousemove', capture, false);
document.getElementById("reset").addEventListener("click",function(){ clearCanvas(canvas);}, false);
document.getElementById("redraw").addEventListener("click", function(){
autoDraw();
}, false);
}
function clearCanvas(canvas){
context.save();
// Use the identity matrix while clearing the canvas
context.setTransform(1, 0, 0, 1, 0, 0);
context.clearRect(0, 0, canvas.width, canvas.height);
// Restore the transform
context.restore();
};
function capture(event){
if(event.which !== 1){
return;
}
tempPos = getMousePos(canvas, event);
x = tempPos.x;
y = tempPos.y;
switch(event.type){
case 'mousedown':
painter.startPaint(event);
break;
case 'mouseup':
painter.endPaint(event);
break;
case 'mousemove':
painter.paint(event);
break;
}
};
var Painter = function(){
var self = this;
self.paintStarted = false;
//this keeps track of whether or not we are currently auto drawing
self.currentlyAutoDrawing = false;
self.startPaint = function(event){
self.resetRecordingParams();
self.paintStarted = true;
context.beginPath();
context.moveTo(x,y);
self.record();
}
self.endPaint = function(event){
self.paintStarted = false;
self.record();
self.paint(event);
}
self.paint = function(event){
if(self.paintStarted){
context.lineTo(x,y);
context.stroke();
self.record();
}
}
self.record = function(){
xarray[xCounter++] = x;
yarray[yCounter++] = y;
}
self.resetRecordingParams = function(){
xarray = [];
yarray = [];
xCounter = 0;
yCounter= 0;
}
return self;
}
function autoDraw(){
context.beginPath();
//If we are already auto-drawing, then we should just return instead of starting another drawing loop cycle
if(painter.currentlyAutoDrawing){
console.log("painter is already auto drawing");
return;
}
painter.currentlyAutoDrawing = true;
console.log('starting at: '+xarray[0]+','+yarray[0]);
context.moveTo(xarray[0],yarray[0]);
for (var i = 0; i < xarray.length; i++) {
setTimeout(drawLineSlowly, 1000+(i*20), i);
};
}
function drawLineSlowly(i)
{
//when we reach the last element in the array, update painter with the fact that autodrawing is now complete
if(xarray.length == i+1){
painter.currentlyAutoDrawing=false;
}
console.log(xarray.length+" "+i);
context.lineTo(xarray[i],yarray[i]);
context.stroke();
}
function getMousePos(canv, evt) {
var rect = canv.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
};
}
init();
});

Obviously you don't stop the previous timeout loop before you start a new...
Use setInterval instead of setTimeout, and clearInterval by next push. So I think the problem is not with the canvas, just with your redraw animation. Btw it is strange because there is some difference between the redraw and the original draw...
var drawInterval = null;
function autoDraw(){
if (drawInterval) {
//here your can reset the previous - still running - redraw
clearInterval(drawInterval);
}
context.beginPath();
console.log('starting at: '+xarray[0]+','+yarray[0]);
context.moveTo(xarray[0],yarray[0]);
var i=0;
setInterval(function (){
++i;
if (i<xarray.length)
drawLineSlowly(i);
else
clearInterval(drawInterval);
},20);
}
note:
There is still bug in the redraw, but at least it does not kill the browser...
Btw the strange "animation" is because you does not check by redraw if you are currently drawing or not, so you start draw and redraw together and they interfere... You have to stop redraw when you start drawing.