小程序内嵌页面，进行分享如何动态设置标题？

onShareAppMessage(options) {

    //console.log(options)

    var that = this

    var return_url = options.webViewUrl

    var path = ‘/pages/index/index?return_url=’ + encodeURIComponent(return_url)

    return {

      title: ‘’,

      path: path,

      success: function (res) {

        that.web_url = return_url

        // 转发成功

        wx.showToast({

          title: “转发成功”,

          icon: ‘success’,

          duration: 2000

        })

      },

      fail: function (res) {

        // 转发失败

      }

    }

  }

，web-view分享标题如何动态设置？？？