JSAPI下单

除付款码支付场景以外，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按Native、JSAPI、APP等不同场景生成交易串调起支付。 官方文档

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

wxpay.v3.pay.transactions.jsapi.post({
  mchid,
  appid,
  description,
  out_trade_no,
  notify_url,
  amount: { total, currency },
  payer: { openid },
})
.then(({ data: { prepay_id } }) => {
  const nonceStr = Formatter.nonce();
  const timeStamp = '' + Formatter.timestamp();
  const packageStr = 'prepay_id=' + prepay_id;
  return { 
    appId,
    timeStamp,
    nonceStr,
    package: packageStr,
    signType: 'RSA',
    paySign: Rsa.sign(
      Formatter.joinedByLineFeed(appId, timeStamp, nonceStr, packageStr),
      merchantPrivateKeyInstance
    )
  }
})