你后台用的nodejs？如果是的话试试这

const qs = require(‘querystring’);

const request = require(‘request’);

router.get(‘openid’,function(req, res) => {

        var data = {

            ‘appid’: appid,//你的appid

            ‘secret’: secret,//你的secret

            ‘js_code’: req.query.code,

            ‘grant_type’: ‘authorization_code’

        };

        var content = qs.stringify(data);

        var url = 'https://api.weixin.qq.com/sns/jscode2session?’ + content;

request.get({

            ‘url’: url

        }, (error, response, body) => {

   // 处理结果

    let body= JSON.parse(body);

    })

})