JS+CSS+HTML实现“代码雨”类似黑客帝国文字下落效果

(function() {
  var lastTime = 0;
  var vendors = ['ms', 'moz', 'webkit', 'o'];
  for (var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
    window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
    window.cancelAnimationFrame = window[vendors[x] + 'CancelAnimationFrame'] ||
      window[vendors[x] + 'CancelRequestAnimationFrame'];
  }
  if (!window.requestAnimationFrame)
    window.requestAnimationFrame = function(callback, element) {
      var currTime = new Date().getTime();
      var timeToCall = Math.max(0, 16 - (currTime - lastTime));
      var id = window.setTimeout(function() {
          callback(currTime + timeToCall);
        },
        timeToCall);
      lastTime = currTime + timeToCall;
      return id;
    };
  if (!window.cancelAnimationFrame)
    window.cancelAnimationFrame = function(id) {
      clearTimeout(id);
    };
}());
// stats
var stats = new Stats();
stats.setMode(0);
stats.domElement.style.position = 'absolute';
stats.domElement.style.left = '0px';
stats.domElement.style.top = '0px';
document.body.appendChild(stats.domElement);
var M = {
  settings: {
    COL_WIDTH: 20,
    COL_HEIGHT: 25,
    VELOCITY_PARAMS: {
      min: 4,
      max: 8
    },
    CODE_LENGTH_PARAMS: {
      min: 20,
      max: 40
    }
  },
  animation: null,
  c: null,
  ctx: null,
  lineC: null,
  ctx2: null,
  WIDTH: window.innerWidth,
  HEIGHT: window.innerHeight,
  COLUMNS: null,
  canvii: [],
  font: '30px matrix-code',
  letters: ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '$', '+', '-', '*', '/', '=', '%', '"', '\'', '#', '&', '_', '(', ')', ',', '.', ';', ':', '?', '!', '\\', '|', '{', '}', '<', '>', '[', ']', '^', '~'],
  codes: [],
  createCodeLoop: null,
  codesCounter: 0,
  init: function() {
    M.c = document.getElementById('canvas');
    M.ctx = M.c.getContext('2d');
    M.c.width = M.WIDTH;
    M.c.height = M.HEIGHT;
    M.ctx.shadowBlur = 0;
    M.ctx.fillStyle = '#000';
    M.ctx.fillRect(0, 0, M.WIDTH, M.HEIGHT);
    M.ctx.font = M.font;
    M.COLUMNS = Math.ceil(M.WIDTH / M.settings.COL_WIDTH);
    for (var i = 0; i < M.COLUMNS; i++) {
      M.codes[i] = [];
      M.codes[i][0] = {
        'open': true,
        'position': {
          'x': 0,
          'y': 0
        },
        'strength': 0
      };
    }
    M.loop();
    M.createLines();
    M.createCode();
    // not doing this, kills CPU
    // M.swapCharacters();
    window.onresize = function() {
      window.cancelAnimationFrame(M.animation);
      M.animation = null;
      M.ctx.clearRect(0, 0, M.WIDTH, M.HEIGHT);
      M.codesCounter = 0;
      M.ctx2.clearRect(0, 0, M.WIDTH, M.HEIGHT);
      M.WIDTH = window.innerWidth;
      M.HEIGHT = window.innerHeight;
      M.init();
    };
  },
  loop: function() {
    M.animation = requestAnimationFrame(function() {
      M.loop();
    });
    M.draw();
    stats.update();
  },
  draw: function() {
    var velocity, height, x, y, c, ctx;
    // slow fade BG colour
    M.ctx.shadowColor = 'rgba(0, 0, 0, 0.5)';
    M.ctx.fillStyle = 'rgba(0, 0, 0, 0.5)';
    M.ctx.fillRect(0, 0, M.WIDTH, M.HEIGHT);
    M.ctx.globalCompositeOperation = 'source-over';
    for (var i = 0; i < M.COLUMNS; i++) {
      // check member of array isn't undefined at this point
      if (M.codes[i][0].canvas) {
        velocity = M.codes[i][0].velocity;
        height = M.codes[i][0].canvas.height;
        x = M.codes[i][0].position.x;
        y = M.codes[i][0].position.y - height;
        c = M.codes[i][0].canvas;
        ctx = c.getContext('2d');
        M.ctx.drawImage(c, x, y, M.settings.COL_WIDTH, height);
        if ((M.codes[i][0].position.y - height) < M.HEIGHT) {
          M.codes[i][0].position.y += velocity;
        } else {
          M.codes[i][0].position.y = 0;
        }
      }
    }
  },
  createCode: function() {
    if (M.codesCounter > M.COLUMNS) {
      clearTimeout(M.createCodeLoop);
      return;
    }
    var randomInterval = M.randomFromInterval(0, 100);
    var column = M.assignColumn();
    if (column) {
      var codeLength = M.randomFromInterval(M.settings.CODE_LENGTH_PARAMS.min, M.settings.CODE_LENGTH_PARAMS.max);
      var codeVelocity = (Math.random() * (M.settings.VELOCITY_PARAMS.max - M.settings.VELOCITY_PARAMS.min)) + M.settings.VELOCITY_PARAMS.min;
      var lettersLength = M.letters.length;
      M.codes[column][0].position = {
        'x': (column * M.settings.COL_WIDTH),
        'y': 0
      };
      M.codes[column][0].velocity = codeVelocity;
      M.codes[column][0].strength = M.codes[column][0].velocity / M.settings.VELOCITY_PARAMS.max;
      for (var i = 1; i <= codeLength; i++) {
        var newLetter = M.randomFromInterval(0, (lettersLength - 1));
        M.codes[column][i] = M.letters[newLetter];
      }
      M.createCanvii(column);
      M.codesCounter++;
    }
    M.createCodeLoop = setTimeout(M.createCode, randomInterval);
  },
  createCanvii: function(i) {
    var codeLen = M.codes[i].length - 1;
    var canvHeight = codeLen * M.settings.COL_HEIGHT;
    var velocity = M.codes[i][0].velocity;
    var strength = M.codes[i][0].strength;
    var text, fadeStrength;
    var newCanv = document.createElement('canvas');
    var newCtx = newCanv.getContext('2d');
    newCanv.width = M.settings.COL_WIDTH;
    newCanv.height = canvHeight;
    for (var j = 1; j < codeLen; j++) {
      text = M.codes[i][j];
      newCtx.globalCompositeOperation = 'source-over';
      newCtx.font = '30px matrix-code';
      if (j < 5) {
        newCtx.shadowColor = 'hsl(104, 79%, 74%)';
        newCtx.shadowOffsetX = 0;
        newCtx.shadowOffsetY = 0;
        newCtx.shadowBlur = 10;
        newCtx.fillStyle = 'hsla(104, 79%, ' + (100 - (j * 5)) + '%, ' + strength + ')';
      } else if (j > (codeLen - 4)) {
        fadeStrength = j / codeLen;
        fadeStrength = 1 - fadeStrength;
        newCtx.shadowOffsetX = 0;
        newCtx.shadowOffsetY = 0;
        newCtx.shadowBlur = 0;
        newCtx.fillStyle = 'hsla(104, 79%, 74%, ' + (fadeStrength + 0.3) + ')';
      } else {
        newCtx.shadowOffsetX = 0;
        newCtx.shadowOffsetY = 0;
        newCtx.shadowBlur = 0;
        newCtx.fillStyle = 'hsla(104, 79%, 74%, ' + strength + ')';
      }
      newCtx.fillText(text, 0, (canvHeight - (j * M.settings.COL_HEIGHT)));
    }
    M.codes[i][0].canvas = newCanv;
  },
  swapCharacters: function() {
    var randomCodeIndex;
    var randomCode;
    var randomCodeLen;
    var randomCharIndex;
    var newRandomCharIndex;
    var newRandomChar;
    for (var i = 0; i < 20; i++) {
      randomCodeIndex = M.randomFromInterval(0, (M.codes.length - 1));
      randomCode = M.codes[randomCodeIndex];
      randomCodeLen = randomCode.length;
      randomCharIndex = M.randomFromInterval(2, (randomCodeLen - 1));
      newRandomCharIndex = M.randomFromInterval(0, (M.letters.length - 1));
      newRandomChar = M.letters[newRandomCharIndex];
      randomCode[randomCharIndex] = newRandomChar;
    }
    M.swapCharacters();
  },
  createLines: function() {
    M.linesC = document.createElement('canvas');
    M.linesC.width = M.WIDTH;
    M.linesC.height = M.HEIGHT;
    M.linesC.style.position = 'absolute';
    M.linesC.style.top = 0;
    M.linesC.style.left = 0;
    M.linesC.style.zIndex = 10;
    document.body.appendChild(M.linesC);
    var linesYBlack = 0;
    var linesYWhite = 0;
    M.ctx2 = M.linesC.getContext('2d');
    M.ctx2.beginPath();
    M.ctx2.lineWidth = 1;
    M.ctx2.strokeStyle = 'rgba(0, 0, 0, 0.7)';
    while (linesYBlack < M.HEIGHT) {
      M.ctx2.moveTo(0, linesYBlack);
      M.ctx2.lineTo(M.WIDTH, linesYBlack);
      linesYBlack += 5;
    }
    M.ctx2.lineWidth = 0.15;
    M.ctx2.strokeStyle = 'rgba(255, 255, 255, 0.7)';
    while (linesYWhite < M.HEIGHT) {
      M.ctx2.moveTo(0, linesYWhite + 1);
      M.ctx2.lineTo(M.WIDTH, linesYWhite + 1);
      linesYWhite += 5;
    }
    M.ctx2.stroke();
  },
  assignColumn: function() {
    var randomColumn = M.randomFromInterval(0, (M.COLUMNS - 1));
    if (M.codes[randomColumn][0].open) {
      M.codes[randomColumn][0].open = false;
    } else {
      return false;
    }
    return randomColumn;
  },
  randomFromInterval: function(from, to) {
    return Math.floor(Math.random() * (to - from + 1) + from);
  },
  snapshot: function() {
    window.open(M.c.toDataURL());
  }
};
function eventListenerz() {
  var controlToggles = document.getElementsByClassName('toggle-info');
  var controls = document.getElementById('info');
  var snapshotBtn = document.getElementById('snapshot');
  function toggleControls(e) {
    e.preventDefault();
    controls.className = controls.className === 'closed' ? '' : 'closed';
  }
  for (var j = 0; j < 2; j++) {
    controlToggles[j].addEventListener('click', toggleControls, false);
  }
  snapshotBtn.addEventListener('click', M.snapshot, false);
}
window.onload = function() {
  M.init();
  eventListenerz();
};

@import url("http://fonts.googleapis.com/css?family=Carrois+Gothic");
@font-face {
  font-family: 'matrix-code';
  src: url('http://neilcarpenter.com/demos/canvas/matrix/font/matrix-code.eot?#iefix') format('embedded-opentype'), url('http://neilcarpenter.com/demos/canvas/matrix/font/matrix-code.woff') format('woff'), url('http://neilcarpenter.com/demos/canvas/matrix/font/matrix-code.ttf') format('truetype'), url('http://neilcarpenter.com/demos/canvas/matrix/font/matrix-code.svg#svgFontName') format('svg');
}
html,
body {
  -webkit-font-smoothing: antialiased;
  font: normal 12px/14px "Carrois Gothic", sans-serif;
  width: 100%;
  height: 100%;
  margin: 0;
  overflow: hidden;
  color: #fff;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}
body {
  background: black;
}
#stats {
  z-index: 100;
}
#info {
  background: rgba(0, 0, 0, 0.7);
  position: fixed;
  bottom: 0;
  left: 0px;
  width: 250px;
  padding: 10px 20px 20px;
  z-index: 100;
  -webkit-transform-origin: bottom center;
  -moz-transform-origin: bottom center;
  -o-transform-origin: bottom center;
  transform-origin: bottom center;
  -webkit-transform: rotate(0deg);
  -moz-transform: rotate(0deg);
  -o-transform: rotate(0deg);
  transform: rotate(0deg);
  -webkit-transition: -webkit-transform .5s ease-in-out;
  -moz-transition: -moz-transform .5s ease-in-out;
  -o-transition: -o-transform .5s ease-in-out;
  transition: transform .5s ease-in-out;
}
#info.closed {
  -webkit-transform: rotate(180deg);
  -moz-transform: rotate(180deg);
  -o-transform: rotate(180deg);
  transform: rotate(180deg);
}
.toggle-info {
  position: absolute;
  display: block;
  height: 10px;
  background: rgba(0, 0, 0, 0.8);
  width: 290px;
  left: 0;
  text-align: center;
  padding: 3px 0 7px;
  text-decoration: none;
  color: white;
  text-shadow: none;
}
.toggle-info:hover {
  background: rgb(0, 0, 0);
}
#close {
  top: -20px;
}
#open {
  bottom: -20px;
  -webkit-transform: rotate(-180deg);
  -moz-transform: rotate(-180deg);
  -o-transform: rotate(-180deg);
  transform: rotate(-180deg);
}
button {
  background: rgba(255, 255, 255, 0.2);
  color: #fff;
  border: 0;
  border-radius: 2px;
  padding: 7px 10px;
  box-shadow: 0 0 3px 0px rgba(255, 255, 255, 0.3);
  cursor: pointer;
}
button:hover {
  background: rgba(255, 255, 255, 0.1);
}
pa {
  color: #fff;
}
pa:hover {
  color: #EFFDEB;
  text-shadow: 0px 0px 5px #75AD61;
}