黑客帝国纯js版

　　明天就回家过年了，今天没什么心思上班，看了下博客，发现一个黑客帝国额js版本，地址：https://blog.csdn.net/zhongyi_yang/article/details/53841805
　　然后做了一点封装，这里也贴出来分享一下：
<!DOCTYPE html>
<html>
<head lang="zh-cn">
    <meta http-equiv=Content-Type content="text/html; charset=utf-8">

    <title>简单的黑客帝国效果</title>
</head>

<body style="height:2000px">
    <script type="text/javascript">
        (function (window) {
            var hackerCache = {};

            //默认配置
            function makeCfg(cfg) {
                cfg = cfg || {};
                var _cfg = {
                    canvas: "hacker_matrix" + ((Math.random() * 10000) >> 0),
                    height: window.innerHeight,
                     window.innerWidth,
                    fontSize: 16,
                    fontColor: "#0F0",
                    fontSyle: "16px arial",
                    seeds: "0123456789abcdefghijklmnopqrstuvwxyz",
                    fillStyle: 'rgba(0, 0, 0, 0.05)',//这里只能是rgba格式,好像用ctx.globalAlpha也能做透明度
                    breaks: 0.98
                };
                for (var key in _cfg) {
                    _cfg[key] = cfg[key] || _cfg[key];
                }

                return _cfg;
            }

            function hacker(cfg) {
                cfg = makeCfg(cfg);

                var canvas = document.getElementById(cfg.canvas);
                //高度及初始化
                var altitudes = [], ctx, texts = cfg.seeds.split('');

                if (!canvas) {
                    canvas = document.createElement("canvas");
                    canvas.id = cfg.canvas;
                    canvas.height = cfg.height;
                    canvas.width = cfg.width;
                    document.body.appendChild(canvas);
                }

                var cache = hackerCache[canvas.id];
                if (!cache) {
                    ctx = canvas.getContext('2d');

                    var columns = canvas.width / cfg.fontSize;
                    for (var i = 0; i < columns; i++) {
                        altitudes[i] = 1;
                    }
                    hackerCache[canvas.id] = {
                        context: ctx,
                        altitudes: altitudes,
                        interval: undefined
                    }

                    cache = hackerCache[canvas.id];
                }

                altitudes = cache.altitudes;
                ctx = cache.context;

                //逐行输出
                function drawLine() {
                    ctx.fillStyle = cfg.fillStyle;
                    ctx.fillRect(0, 0, canvas.width, canvas.height);

                    //文字颜色
                    ctx.fillStyle = cfg.fontColor;
                    ctx.font = cfg.fontSyle;

                    for (var i = 0; i < altitudes.length; i++) {
                        var altitude = altitudes[i];
                        var y = altitude * cfg.fontSize;

                        var text = texts[Math.floor(Math.random() * texts.length)];
                        ctx.fillText(text, i * cfg.fontSize, y);

                        if (y > canvas.height && Math.random() > cfg.breaks) {
                            altitude = 0;
                        }

                        altitudes[i] = ++altitude;
                    }
                }

                this.start = function () {
                    if (cache.interval === undefined) {
                        cache.interval = setInterval(function () {
                            drawLine();
                        }, 33);
                    }
                };
                this.stop = function () {
                    cache.interval = cache.interval && clearInterval(cache.interval);
                }
            }

            window.hacker = hacker;
        })(window);

        window.onload = function () {
            //new hacker().start();
            new hacker({ canvas: "canvas1" }).start();
            new hacker({ canvas: "canvas2" }).start();
            new hacker({ canvas: "canvas3" }).start();
            new hacker({ canvas: "canvas4" }).start();
        }
    </script>
    <canvas id="canvas1" width="400" height="400"></canvas>
    <canvas id="canvas2" width="400" height="400"></canvas>
    <canvas id="canvas3" width="400" height="400"></canvas>
    <canvas id="canvas4" width="400" height="400"></canvas>
</body>
</html>