小程序中用到了扫描二维码打开指定的小程序页面功能，微信提供了指定页面的二维码生成借口，但是返回的不是二维码的网络地址，需要服务端转存一下;用node搞了一下
API地址

接口需要access_token，请求access_token涉及到appid,secret就没把代码贴出来；用下面的接口获取access_token，GET请求;懒得写代码的直接扔到浏览器获取即可；

https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=APPID&secret=APPSECRET

直接上货

var http = require("http"),
fs = require("fs"),
data = {"path": "pages/homePage/homePage", "width": 430};
data = JSON.stringify(data);
var options = {
    method: "POST",
    host: "api.weixin.qq.com",
    path: "/cgi-bin/wxaapp/createwxaqrcode?access_token=5-R9rTlaeHF9bdZPWWh-t9BefbthRfbe5idSzuOSXoSFfPcUOUcTca1QhLNjDVclBK489LX88-hUeT1kL9FV8GBR4fWY78PVxyx_OGnNbJsUEQgAAACMY",
//记得更换token token有效时间2h
    headers: {
        "Content-Type": "application/json",
        "Content-Length": data.length
    }
};
var req = http.request(options, function (res) {
    res.setEncoding("binary");
  var imgData = "";
  res.on('data', function (chunk) {
      imgData += chunk;
  });
  res.on("end", function () {
      fs.writeFile("./wx_liteQR.jpeg", imgData, "binary", function (err) {
            if (err) {
                console.log("down fail");
            }
            console.log("down success");
        });
    });
});
req.write(data);
req.end();