APP下单

商户系统先调用该接口在微信支付服务后台生成预支付交易单，返回正确的预支付交易会话标识后再在APP里面调起支付。 官方文档

const { Formatter, Rsa } = require('wechatpay-axios-plugin')

wxpay.v3.pay.transactions.app.post({
  mchid,
  appid,
  description,
  out_trade_no,
  notify_url,
  amount: { total, currency },
})
.then(({ data: { prepay_id: prepayid } }) => {
  const noncestr = Formatter.nonce();
  const timestamp = '' + Formatter.timestamp();
  return { 
    appid,
    partnerid,
    prepayid,
    noncestr,
    timestamp,
    package: 'Sign=WXPay',
    sign: Rsa.sign(
      Formatter.joinedByLineFeed(appid, timestamp, noncestr, prepayid),
      merchantPrivateKeyInstance
    )
  }
})