第三方平台模式，wx.getExtConfigSync获取不到参数？

if (wx.getExtConfig) {

var extConfig = wx.getExtConfigSync();

this.globalData.hosts = extConfig.hosts;

this.globalData.imghosts = extConfig.imghosts;

this.globalData.mini_program_id = extConfig.mini_program_id;

}

求官方解释下疑惑