vant-weapp/packages/noticebar/index.js

const ZanNoticeBar = {
  initZanNoticeBarScroll(componentId) {
    this.zanNoticeBarNode = this.zanNoticeBarNode || {};
    this.zanNoticeBarNode[`${componentId}`] = {
      width: undefined,
      wrapWidth: undefined,
      animation: null,
      resetAnimation: null
    };

    const currentComponent = this.zanNoticeBarNode[`${componentId}`];
    wx.createSelectorQuery()
      .in(this)
      .select(`#${componentId}__content`)
      .boundingClientRect((rect) => {
        if (!rect || !rect.width) {
          console.warn('页面缺少 noticebar 元素');
          return;
        }

        currentComponent.width = rect.width;
        wx
          .createSelectorQuery()
          .in(this)
          .select(`#${componentId}__content-wrap`)
          .boundingClientRect((rect) => {
            if (!rect || !rect.width) {
              return;
            }

            clearTimeout(this.data[componentId].setTimeoutId)

            currentComponent.wrapWidth = rect.width;
            if (currentComponent.wrapWidth < currentComponent.width) {
              var mstime = currentComponent.width / 40 * 1000;
              currentComponent.animation = wx.createAnimation({
                duration: mstime,
                timingFunction: 'linear'
              });
              currentComponent.resetAnimation = wx.createAnimation({
                duration: 0,
                timingFunction: 'linear'
              });
              this.scrollZanNoticeBar(componentId, mstime);
            }
          })
        .exec();
      })
    .exec();
  },

  scrollZanNoticeBar(componentId, mstime) {
    const currentComponent = this.zanNoticeBarNode[`${componentId}`];
    const resetAnimationData = currentComponent.resetAnimation.translateX(currentComponent.wrapWidth).step();
    this.setData({
      [`${componentId}.animationData`]: resetAnimationData.export()
    });
    const aninationData = currentComponent.animation.translateX(-mstime * 40 / 1000).step();
    setTimeout(() => {
      this.setData({
        [`${componentId}.animationData`]: aninationData.export()
      });
    }, 100);

    const setTimeoutId = setTimeout(() => {
      this.scrollZanNoticeBar(componentId, mstime);
    }, mstime);
    this.setData({
      [`${componentId}.setTimeoutId`]: setTimeoutId
    })
  }
};

module.exports = ZanNoticeBar;