I am trying to plete This tutorial on making a tic tac toe game using JavaScript and HTML5.
I've followed each step in the video multiple times. While my code seems to match the code in video I keep encountering an error: Uncaught Reference Error: draw is not defined. The error occurs in line 12.
I must be overlooking something. Can anyone point it out?
<!DOCTYPE html>
<html>
<head>
<title>Tic Tac Toe!</title>
<script type="text/javascript">
var c, canvas;
var turn = 1;
window.onload = function() {
canvas = document.getElementById("canvas");
c = canvas.getContext("2d");
draw();
}
var moves = [];
window.onclick = function(e) {
if(e.pageX < 500 && e.pageY < 500) {
var cX = Math.floor(e.pageX / (500 / 3));
var cY = Math.floor(e.pageY / (500 / 3));
var alreadyClicked = false;
for(i in moves) {
if(moves[i][0] == cX && moves[i][1] == cY) {
alreadyClicked = true;
}
}
if(alreadyClicked == false) {
moves[(moves.length)] = [cX, cY, turn];
turn = turn * -1;
draw();
}
}
var bg = new Image();
var x = new Image();
var o = new Image();
bg.src = "ttt_board.png";
x.src = "ttt_x.png";
o.src = "ttt_o.png";
function draw() {
c.clearRect(0, 0, 500, 500);
c.drawImage(bg, 0, 0);
for(i in moves) {
if(moves[i][2] == 1) {
c.drawImage(x, Math.floor(moves[i][0] * (500 / 3) + 10), Math.floor(moves[i][1](500 / 3) + 10))
} else {
c.drawImage(o, Math.floor(moves[i][0] * (500 / 3) + 10), Math.floor(moves[i][1] * (500 / 3) + 10));
}
}
}
};
</script>
</head>
<body>
<canvas id="canvas" width="500px" height="500px"></canvas>
</body>
</html>
I am trying to plete This tutorial on making a tic tac toe game using JavaScript and HTML5.
I've followed each step in the video multiple times. While my code seems to match the code in video I keep encountering an error: Uncaught Reference Error: draw is not defined. The error occurs in line 12.
I must be overlooking something. Can anyone point it out?
<!DOCTYPE html>
<html>
<head>
<title>Tic Tac Toe!</title>
<script type="text/javascript">
var c, canvas;
var turn = 1;
window.onload = function() {
canvas = document.getElementById("canvas");
c = canvas.getContext("2d");
draw();
}
var moves = [];
window.onclick = function(e) {
if(e.pageX < 500 && e.pageY < 500) {
var cX = Math.floor(e.pageX / (500 / 3));
var cY = Math.floor(e.pageY / (500 / 3));
var alreadyClicked = false;
for(i in moves) {
if(moves[i][0] == cX && moves[i][1] == cY) {
alreadyClicked = true;
}
}
if(alreadyClicked == false) {
moves[(moves.length)] = [cX, cY, turn];
turn = turn * -1;
draw();
}
}
var bg = new Image();
var x = new Image();
var o = new Image();
bg.src = "ttt_board.png";
x.src = "ttt_x.png";
o.src = "ttt_o.png";
function draw() {
c.clearRect(0, 0, 500, 500);
c.drawImage(bg, 0, 0);
for(i in moves) {
if(moves[i][2] == 1) {
c.drawImage(x, Math.floor(moves[i][0] * (500 / 3) + 10), Math.floor(moves[i][1](500 / 3) + 10))
} else {
c.drawImage(o, Math.floor(moves[i][0] * (500 / 3) + 10), Math.floor(moves[i][1] * (500 / 3) + 10));
}
}
}
};
</script>
</head>
<body>
<canvas id="canvas" width="500px" height="500px"></canvas>
</body>
</html>
-
5
I've properly indented your javascript. Now it should be obvious why the function is not defined (different scopes). Besides that: Please make sure all your loop variables are local (using e.g.
var i;)! – ThiefMaster Commented Sep 24, 2013 at 14:11 - Properly ? Not even close :o – Virus721 Commented Sep 24, 2013 at 14:23
3 Answers
Reset to default 3The problem is that draw is defined in window.onclick, but you are trying to call it from window.onload. Are you sure you do not have a closing bracket missing before the definition of draw?
Try moving the draw() function out of the window.click function.
window.onclick = function(e) {
// ...
};
function draw() {
// ...
}
One of the major benefits of being strict with your indentation is that you can pick up these bugs very quickly.
window.click = function(e) {
// ...
function draw() {
// ...
}
};
Is the code you had.
As a result of draw being located inside of the window.onclick anonymous function, it is scoped there. Since window.onload does not share the scope of that anonymous function, you cannot access draw from window.onload. You should removed the draw function from your window.onclick event so that it may be called from other scopes.
function draw(){}
window.onload = function(){ /*code*/ };
window.onclick = function(){ /* code */ };