<div id="box" class="box"></div>
 <input type="text" id="txt" />
 <button onclick="send()">提交内容</button>

 function $(str) {
  return document.getElementById(str);
 }
 function send() {
  var word = $('txt').value;
  var span = document.createElement('span');
  var top = parseInt(Math.random() * 500) - 20;
  var color1 = parseInt(Math.random() * 256);
  var color2 = parseInt(Math.random() * 256);
  var color3 = parseInt(Math.random() * 256);
  var color = "rgb(" + color1 + "," + color2 + "," + color3 + ")";
  top = top < 0 ? 0 : top;
  span.style.position = 'absolute';
  span.style.top = top + "px";
  span.style.color = color;
  span.style.left = '500px';
  span.style.whiteSpace = 'nowrap';
  var nub = (Math.random() * 10) + 1;
  span.setAttribute('speed', nub);
  span.speed = nub;
  span.innerHTML = word;
  $('box').appendChild(span);
  $('txt').value = "";
 }
 setInterval(move, 200);
 function move() {
  var spanArray = $('box').children;
  for (var i = 0; i < spanArray.length; i++) {
   spanArray[i].style.left =
    parseInt(spanArray[i].style.left) - spanArray[i].speed + 'px';
  }
 }

 var color1 = parseInt(Math.random() * 256);
 var color2 = parseInt(Math.random() * 256);
 var color3 = parseInt(Math.random() * 256);
 var color = "rgb(" + color1 + "," + color2 + "," + color3 + ")";
 span.style.color = color;

var top = parseInt(Math.random() * 500) - 20;
top = top < 0 ? 0 : top;
span.style.top = top + "px";

 span.style.left = '500px';
 setInterval(move, 200);
 function move() {
  var spanArray = $('box').children;
  for (var i = 0; i < spanArray.length; i++) {
   spanArray[i].style.left =
    parseInt(spanArray[i].style.left) - spanArray[i].speed + 'px';
  }
 }