WeChat Payment Notes.

gistfile1.txt

// when your webapp is loaded, before adding listener for weixing js bridge, check if it's already initialized:
var timeoutID = 0;

if (typeof WeixinJSBridge == "undefined") {
  alert('Already in WeChat!');
} else {
  // setup a time out of let's say 5 seconds, to wait for the bridge:
  timeoutID = window.setTimeout(WeChatBridgeTimeout, 5000);
  // now add listener for the bridge:
  document.addEventListener('WeixinJSBridgeReady', WeChatBridgeReady, false);
}

// Now in bridge time out:
function WeChatBridgeTimeout() {
 // Just to be sure that bridge was not initialized just before the line we added the listener (since it's a separate process than JS), let's check for it again:
  if (typeof WeixinJSBridge !== "undefined") {
    alert('Yes, we are finally in WeChat!');
  } else {
    alert('Seems we are out of WeChat');
  }
}

// And in event handled:
function WeChatBridgeReady() {
  // remove listener timeout
  window.clearTimeout(timeoutID);
  alert('Yes, we jumped into WeChat!');
  // WeChat JS bridge initialized.
}

// Deal with Redirect

/**
 * GET params by its name
 * @param  {String} name Name of the GET param
 * @param  {String} url  URL to parse, otherwise use current url
 * @return {String}      Value of the GET param
 */
function getParameterByName(name, url) {
  url = url || window.location.href;
  name = name.replace(/[\[\]]/g, "\\$&");
  let regex = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)");
  let results = regex.exec(url);
  if (!results) return null;
  if (!results[2]) return '';
  return decodeURIComponent(results[2].replace(/\+/g, " "));
}

// OAuth

if (getParameterByName('state')) {
  alert('Code: ' + getParameterByName('code') + ' State: ' + getParameterByName('state'));
} else {
  location.href = 'https://open.weixin.qq.com/connect/oauth2/authorize?appid=wx608050d8426ae8ce&redirect_uri=http%3A%2F%2Fjoyseeedu.cn%2Fwechat-auth-test%2F&response_type=code&scope=snsapi_base&state=joyseelogin#wechat_redirect';
}

// Get Access Token

// let code = getParameterByName('code');
// let url = 'https://api.weixin.qq.com/sns/oauth2/access_token?appid=wx608050d8426ae8ce&secret=<SECRET>&code=' + code + '&grant_type=authorization_code';

// let request = new XMLHttpRequest();
// request.open('GET', url, false);  // `false` makes the request synchronous
// request.send(null);

// if (request.status === 200) {
//   alert(request.responseText);
// }
// 

let payargs = { appId: 'wx608050d8426ae8ce',
  timeStamp: '1474526592',
  nonceStr: '6nPDGFyXNMKKhufIpOqzu27L17ucp3zc',
  signType: 'MD5',
  package: 'prepay_id=wx201609221443127be9df85840672782175',
  paySign: 'F80FBEC0EB496219F3E13AC26443C5AF',
  timestamp: '1474526592' };

document.addEventListener('WeixinJSBridgeReady', () => {
  WeixinJSBridge.invoke('getBrandWCPayRequest', payargs, function(res) {
    if (res.err_msg === "get_brand_wcpay_request:ok") {
      alert("支付成功");
      // 这里可以跳转到订单完成页面向用户展示 
    }else{
      alert("支付失败，请重试");
    }
  });

}, false);