wx.request({

    url: "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=" + access_token,

    method: 'POST',

    data: {

    scene: ' ',

    page: 'pages/index/index',

    width: 430,

    auto_color: false,

    line_color: { "r": "0", "g": "0", "b": "0" }

    },

    success: function (res) {

    console.log(res);

    }

})

这里的scene要怎么在小程序获取然后在传给后台呢