docs: function (param, callbackId) {
      if (typeof param === 'string') {
        try {
          param = JSON.parse(param)
        }
        catch (e) {
          return
        }
      }
      if (typeof param !== 'object' || !param.url) {
        return console.error(
          '[h5-render] invalid config or invalid config.url for sendHttp API')
      }
  
      const sender = this.sender
      const method = param.method || 'GET'
      const xhr = new XMLHttpRequest()
      xhr.open(method, param.url, true)
      xhr.onload = function () {
        sender.performCallback(callbackId, this.responseText)
      }
      xhr.onerror = function (error) {
        return console.error('[h5-render] unexpected error in sendHttp API', error)
        // sender.performCallback(
        //   callbackId,
        //   new Error('unexpected error in sendHttp API')
        // )
      }
      xhr.send()
    }