<scroll-view class="container">
 <view class="scrolltxt">
 <view class="marquee_box">
  <view class="marquee_text" style="transform: translateX(-{{marqueeDistance}}px)">
  <text>{{text}}</text>
  <text style="margin-right:{{marquee_margin}}px;"></text>
  <text style="margin-right:{{marquee_margin}}px;">{{text}}</text>  
  </view>
 </view>
 </view>
</scroll-view>

.container {height: 100%;display: flex;flex-direction: column;justify-content: space-between;box-sizing: border-box;}
.scrolltxt{padding:0 20rpx;background:#f8f8f8;}
.marquee_box {position:relative;color:#333;height:90rpx;display:block;overflow:hidden;} 
.marquee_text {white-space: nowrap;position:absolute;top:0;font-size:14px;height:90rpx;line-height:90rpx;}

Page({
 /**
 * 页面的初始数据
 * Linyufan.com
 */
 data: {
 text: "这是一条测试公告，看看效果怎么样，2019年3月23日",
 marqueePace: 1,//滚动速度
 marqueeDistance: 0,//初始滚动距离
 marquee_margin: 30,
 size:14,
 interval: 20 // 时间间隔
 },
 
 /**
 * 生命周期函数--监听页面加载
 */
 onLoad: function (options) { 
 },
 onShow: function () {
 var that = this;
 var length = that.data.text.length * that.data.size;//文字长度
 var windowWidth = wx.getSystemInfoSync().windowWidth;// 屏幕宽度
 //console.log(length,windowWidth);
 that.setData({
  length: length,
  windowWidth: windowWidth
 });
 that.scrolltxt();// 第一个字消失后立即从右边出现
 },
 
 scrolltxt: function () {
 var that = this;
 var length = that.data.length;//滚动文字的宽度
 var windowWidth = that.data.windowWidth;//屏幕宽度
 if (length > windowWidth){
  var interval = setInterval(function () {
  var maxscrollwidth = length + that.data.marquee_margin;//滚动的最大宽度，文字宽度+间距，如果需要一行文字滚完后再显示第二行可以修改marquee_margin值等于windowWidth即可
  var crentleft = that.data.marqueeDistance;
  if (crentleft < maxscrollwidth) {//判断是否滚动到最大宽度
   that.setData({
   marqueeDistance: crentleft + that.data.marqueePace
   })
  }
  else {
   //console.log("替换");
   that.setData({
   marqueeDistance: 0 // 直接重新滚动
   });
   clearInterval(interval);
   that.scrolltxt();
  }
  }, that.data.interval);
 }
 else{
  that.setData({ marquee_margin:"1000"});//只显示一条不滚动右边间距加大，防止重复显示
 } 
 }
})