小程序前端代码

// 登录
login(){
	wx.login({
	  success:loginRes => {
	    if (loginRes.code) {
	     wx.getUserInfo({
	       success: user => {
	     	  uni.request({
	     	  	url:"http://192.168.0.22:8666/wxLogin",
	     		method:"POST",
	     		data:{
	     			code:loginRes.code,
	     			encryptedData:user.encryptedData,
	     			iv:user.iv
	     		},
	     		success:reqRes => {
	     			console.log(reqRes)
	     		}
	     	  })
	       }
	     })
	    } else {
	      console.log('登录失败！' + user.errMsg)
	    }
	  }
	})
}

node代码

需要安装：
npm install crypto-js
npm install js-base64

注意： appid和secret要换掉 切记无脑copy

/**
*封装的工具类（可以直接copy使用）
*
*/ 

const request = require('request')
const CryptoJS = require('crypto-js')
const Base64 = require('js-base64')
const { resolve } = require('path')
class WechatUtil {
    constructor() {
        this.reqUrl = "https://api.weixin.qq.com/sns/jscode2session"
        this.appid = "你的微信小程序appid"
        this.secret = "你的微信小程序secret "
        this.grant_type = "authorization_code"
        this.openId = null
        this.sessionKey = null
    }
    getOpenId(){
        return this.openId
    }
    getSessionKey(){
       return this.sessionKey
    }
    // 获取 sessionKey openid 
    getSessionKeyOropenid(code) {
        return new Promise((resolve, reject) => {
            let url = `${this.reqUrl}?appid=${this.appid}&secret=${this.secret}&js_code=${code}&grant_type=${this.grant_type}`
            request.post(url, {}, (error, res, body) => {
                if (error) {
                    console.error(error)
                    reject(error)
                }
                if(res.statusCode == 200){
                    let jsonBody = JSON.parse(body)
                    this.openId = jsonBody.openId
                    this.sessionKey = jsonBody.session_key
                    resolve(this.sessionKey)
                }
            })
        })
    }
    // 解密获取用户信息
    getWechatUserInfo(encryptedData, ivv, sessionKey) {
        if(!sessionKey){
            sessionKey = this.sessionKey
        }
        let key = CryptoJS.enc.Base64.parse(sessionKey)
        let iv = CryptoJS.enc.Base64.parse(ivv)
        let decrypt = CryptoJS.AES.decrypt(encryptedData, key, {
            iv: iv,
            mode: CryptoJS.mode.CBC,
            padding: CryptoJS.pad.Pkcs7
        })
        return JSON.parse(Base64.decode(CryptoJS.enc.Base64.stringify(decrypt)))
    }
}

module.exports = WechatUtil

调用方式

// 微信小程序登录
const WechatUtil = require("../utils/WechatUtil")
const wechatUtil = new WechatUtil()

router.post("/wxLogin", (req, res, next) => {
    const { code, encryptedData, iv } = req.body
    wechatUtil.getSessionKeyOropenid(code).then(e => {
        // 获取微信用户信息
        const wechatUserInfo = wechatUtil.getWechatUserInfo(encryptedData, iv)
        res.json({
            msg: "登录成功",
            data: wechatUserInfo
        })
    }).catch(err => {
        res.json({
            msg: "授权失败",
            error: err
        })
    })
})

前端请求结果