Javascript error in rails

Question

i start to learn javascript with easy game tutorial http://www.youtube.com/watch?v=U7anheKJSaIand on RoR got error in index.html.erb:

<script>

    var ctx, canvas;
    var data;

    window.onload = function main(){

        canvas = document.createElement("canvas");
        canvas.width = canvas.height = 200;
        ctx = canvas.getContext("2d");

        document.body.appendChild(canvas);
        init();
        tick();
    } 

    function init(){
        data = new Tile(20,20);
    }

    function tick(){
        window.requestAnimationFrame(tick);

        update();
        render();
    }

    function update(){}

    function render(){
        data.draw(ctx);
    }

    function Tile(x,y){
        var x = x, y = y;
        var tile = Tile.BlANK;

        if(tile == null){
            var _c = document.createElement("canvas");
            _c.width = _c.height = 100;
            _ctx = _c.getContext("2d");

            _ctx.fillStyle = "skyblue";
            //blank
            _ctx.fillRect(0,0,100,100);
            Tile.BlANK = new Image();
            Tile.BLANK.src = _c.toDataURL();

            tile = Tile.BLANK;
        }  

    this.update = function(){}  

    this.draw = function(ctx){
        ctx.drawImage(tile, x, y);
    }

}

</script>

and this is error:

Tile.BLANK.src = _c.toDataURL();

Uncaught TypeError: Cannot set property src of undefined

divoom12 · Accepted Answer · 2015-10-12 12:47:26Z

1

Your error is here

Tile.BlANK = new Image();

It should be:

Tile.BLANK = new Image();

The error comes from .BlANK and it's because there is a typo. The l (L) is lowecase, and therefore later when you are trying to access the .src in you can't, because the real .BLANK is still undefined.

This is in function Tile(x,y){...}, but you also have the typo some other places. Just check your code for lowercase letters in .BLANK.

answered Oct 12, 2015 at 12:47

divoom12

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