Lo que estoy tratando de hacer aquí es llamar al nombre de usuario de la base de datos de la cookie, intenté simplemente llamarlo a través de una función normal, pero eso no funciona porque tengo que esperar los datos. luego, después de enviar los datos a la página web. pero mi problema es solo obtener los datos en sí. Realmente no tengo mucha experiencia con las promesas, así que estoy tratando de averiguar qué está pasando aquí. gracias por la ayuda.
async function user(req, res) { let key = req.cookies['cookie'] return new Promise((resolve, reject) => { connection.query('SELECT * FROM accounts WHERE `key` = ?', [key], (error, results, fields) => { if (error) { return console.log(error) } if (results.length > 0) { resolve(results[0].username) } }); } ) } async function grabinfo(req, res) { res.render('dashboard', { title:'Dashboard', username: username}); const username = await user(req, res) } module.exports.grabinfo = grabinfoEl error
(node:1463495) UnhandledPromiseRejectionWarning: ReferenceError: Cannot access 'username' before initialization at Object.grabinfo (/home/ubuntu/nodeprojects/website/modules/dashboard.js:45:58) at /home/ubuntu/nodeprojects/website/router/app.js:37:15 at Layer.handle [as handle_request] (/home/ubuntu/nodeprojects/website/node_modules/express/lib/router/layer.js:95:5) at next (/home/ubuntu/nodeprojects/website/node_modules/express/lib/router/route.js:144:13) at Route.dispatch (/home/ubuntu/nodeprojects/website/node_modules/express/lib/router/route.js:114:3) at Layer.handle [as handle_request] (/home/ubuntu/nodeprojects/website/node_modules/express/lib/router/layer.js:95:5) at /home/ubuntu/nodeprojects/website/node_modules/express/lib/router/index.js:286:22 at Function.process_params (/home/ubuntu/nodeprojects/website/node_modules/express/lib/router/index.js:348:12) at next (/home/ubuntu/nodeprojects/website/node_modules/express/lib/router/index.js:280:10) at SendStream.error (/home/ubuntu/nodeprojects/website/node_modules/serve-static/index.js:121:7) (node:1463495) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli .html#cli_unhandled_rejections_mode). (rejection id: 1) (node:1463495) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections t hat are not handled will terminate the Node.js process with a non-zero exit code.async function grabinfo(req, res) { const username = await user(req, res) res.render('dashboard', { title:'Dashboard', username: username}) }El mensaje de error dice claramente. Está utilizando la constante de nombre de usuario antes de definirla. javascript funciona de arriba a abajo, no de abajo a arriba, así que primero inicialice el nombre de usuario y luego úselo.
async function user(req, res) { let key = req.cookies['cookie'] return new Promise((resolve, reject) => { connection.query('SELECT * FROM accounts WHERE `key` = ?', [key], (error, results, fields) => { if (error) { return console.log(error) } if (results.length > 0) { resolve(results[0].username) } }); } ) } async function grabinfo(req, res) { const username = await user(req, res); res.render('dashboard', { title:'Dashboard', username: username}); } module.exports.grabinfo = grabinfo