报错 err is not defined

来源：10-6 mysql查询开发

幕布斯1065030

2022-05-29

function querySql(sql) {
    const conn = connect();
    return new Promise((resolve, reject) => {
        try {
            conn.query(sql, (err, results => {
                if (err) {
                    reject(err)
                } else {
                    resolve(results)
                }

            }))
        } catch (e) {
            reject(e)
        } finally {
            conn.end(); // 不释放的话，会造成内存泄露
        }
    })
}

报错 err is not defined

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1回答

幕布斯1065030

提问者

2022-05-29

POST /users/login 200 105.378 ms - 31

(node:1876) UnhandledPromiseRejectionWarning: ReferenceError: err is not defined

at H:\desktop\learn\learnnode\myapp\db\index.js:27:30

at new Promise (<anonymous>)

at querySql (H:\desktop\learn\learnnode\myapp\db\index.js:25:12)

at H:\desktop\learn\learnnode\myapp\routes\users.js:22:3

at Layer.handle [as handle_request] (H:\desktop\learn\learnnode\myapp\node_modules\_express@4.16.4@express\lib\router\layer.js:95:5)

at next (H:\desktop\learn\learnnode\myapp\node_modules\_express@4.16.4@express\lib\router\route.js:137:13)

at Route.dispatch (H:\desktop\learn\learnnode\myapp\node_modules\_express@4.16.4@express\lib\router\route.js:112:3)

at Layer.handle [as handle_request] (H:\desktop\learn\learnnode\myapp\node_modules\_express@4.16.4@express\lib\router\layer.js:95:5)

at H:\desktop\learn\learnnode\myapp\node_modules\_express@4.16.4@express\lib\router\index.js:281:22

at Function.process_params (H:\desktop\learn\learnnode\myapp\node_modules\_express@4.16.4@express\lib\router\index.js:335:12)

(Use `node --trace-warnings ...` to show where the warning was created)

(node:1876) 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: 2)

(node:1876) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

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