微信小程序进行微信支付流程图解

/*
 *  功能： 返回32位随机字符串
 *  create by tiankai on 2018-06-25 15:39
 */
getNonceStr(){
    let char = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    let len = 32;
    let result = '';
    for(let i = 0; i < len; i++){
        let randomNum = Math.floor(Math.random()*char.length);
        result += char[randomNum];
    }
    return result;
}

/*
 *  功能：sign 参数签名
 *  create by tiankai on 2018-06-26 12:00
 */
async makeSign(params, key){
    // 生成签名 sign
    let strOrderArr = Object.keys(params).sort();
    let stringA = "";
    strOrderArr.map(val =>{
        //如果参数值为空，或者验证返回的 sign 不参与签名
        if(
            think.isNullOrUndefined(params[val]) ||
            val === 'sign' ||
            params[val].length === 0
        ) return;
        stringA += val + "=" + params[val] + "&";
    });
    let stringSignTemp = stringA + "key=" + key;
    let sign = think.md5(stringSignTemp).toUpperCase();
    return sign;
}

const xml2js = require('xml2js');

//xml->json
//xml2js默认会把子子节点的值变为一个数组, explicitArray设置为false
var xmlParser = new xml2js.Parser({explicitArray : false, ignoreAttrs : true})
//json->xml
var jsonBuilder = new xml2js.Builder();

/*
 *  功能：获取统一下单 API 请求XML参数
 *  create by tiankai on 2018-06-25 15:23
 */
async getUnifiedOrderParams(){
    let signString = {
        appid: config.appid,
        mch_id: config.mchid,
        nonce_str: await this.getNonceStr(),
        body: '短信平台-短信套餐购买',
        out_trade_no: '20180926125346',//订单号
        total_fee: 88,//订单金额
        //APP和网页支付提交用户端ip，Native支付填调用微信支付API的机器IP
        //需要自行获取，这里只是为了测试直接写上了
        spbill_create_ip: '123.12.12.123',
        notify_url: config.notify_url,
        trade_type: 'JSAPI',
        openid: await think.cache('openId')
    }
    let sign = await this.makeSign(signString,config.key);
    signString.sign = sign;
    /* console.log("--------------------------");
     * console.log(sign);
     * console.log("--------------------------"); */
    let xml = await jsonBuilder.buildObject(signString);
    /* console.log(xml); */
    return xml;
}

/*
 *  功能：调用统一下单API接口
 *  create by tiankai on 2018-06-26 11:01
 */
async unifiedOrder(){
    let xmlParams = await this.getUnifiedOrderParams();
    let unifiedOrderUrl = config.unifiedOrderUrl;
    let opt = {
        method: "POST",
        mode: 'cors',
        headers: {
            'content-type': 'text/xml'
        },
        body: xmlParams
    }
    let res = await this.fetch(unifiedOrderUrl, opt);
    //这里微信返回的也是 xml
    let result = await res.text();
    let data = null;
    // 微信返回的 XML 转换为 JSON
    xmlParser.parseString(result,function(err, jsonData){
        if(!err){
            /* console.log(jsonData); */
            data = jsonData;
        }
    });
    return data;
}

/*
 *  功能：统一下单接口返回 prepay_id 再次签名 返回给前端
 *  create by tiankai on 2018-06-26 15:45
 */
async payParams(){
    let signString = {
        appid: config.appid,
        timeStamp: +new Date(),
        nonce_str: await this.getNonceStr(),
        package: null,
        signType: 'MD5'
    }
    //调用 统一下单 API
    let jsonData = await this.unifiedOrder();
    if(think.isNullOrUndefined(jsonData) &&
       jsonData.xml.return_code === 'SUCCESS' &&
       jsonData.xml.result_code === 'SUCCESS'
    ){
        signString.package = 'perpay_id='+jsonData.xml.perpay_id
    }else{
        return jsonData.xml.return_msg;
    }
    //进行再次签名
    let paySign = await this.makeSign(signString,config.key);
    signString.paySign = paySign;
    let { appid, signType, ...result } = signString;
    // result 中不包括 appid 和 signType 返回给前端
    return result;
}

wx.requestPayment({
   'timeStamp': '',
   'nonceStr': '',//后端返回的随机字符串
   'package': '',//后端返回的
   'signType': 'MD5',
   'paySign': '',//后端返回的
   'success':function(res){
   },
   'fail':function(res){
   }
});