不起作用module.exports

Question

文件ConnectToDB

var pg = require("pg");
var dataWithDB = require('./DataBase/ConnectToDb');
var pool = new pg.Pool({
host: "localhost",
port: "5432",
user: "postgres",
password: "111111",
database: "hrs"
});

pool.connect(function (err,client,done) {
if(err)console.log("connect "  + err.toString());

else
    client.query('SELECT id, "idName", "idContact", "idExperience", 
"idSkill", "dateAdded", "dateColloquy"' +
'FROM public."applicant ";',function (err,result) {

        if(err) {
            //console.log("query " + err.toString());
            exports.res = "Data NOT";
        }
        else {
            console.log(result.rows);
            module.exports.resul = result.rows;
        }
        done();
    });

});
pool.end()

文件app.js

var dataWithDB = require('./DataBase/ConnectToDb');

console.log(dataWithDB + "  wit DB");

结果给我推导出了未定义的机智数据库，但应该来自数据库的数据

范围内可以有错误吗？ 如果在文件模块的末尾指定，则发送数据。exporst.result=“ Example”。

Answer 1

这是您应该执行的操作：导入另一个传递给查询的回调函数。 此回调将对结果执行任何您想要的操作。 如所写，您的方法将不起作用并且没有意义。

Answer 2

您应该将连接到数据库的代码封装在需要回调的函数中。

这是一个示例，希望您能理解。 :)

./DataBase/ConnectToDb

var pg = require("pg");
module.exports = (callback) => {
    var pool = new pg.Pool({
        host: "localhost",
        port: "5432",
        user: "postgres",
        password: "111111",
        database: "hrs"
    });

    pool.connect(function (err, client, done) {
        if (err) {
            console.log("connect " + err.toString());
        } else {
            let query = 'SELECT id, "idName", "idContact",' +
                ' "idExperience","idSkill", "dateAdded", "dateColloquy"' +
                'FROM public."applicant ";'
            client.query(query, function (err, result) {
                if (err) {
                    //console.log("query " + err.toString());
                    exports.res = "Data NOT";
                    callback(err);
                }
                else {
                    console.log(result.rows);
                    callback(null, result);
                }
                done(); // Not sure what this does! :-o
            });
        }
    });
    // Is this trying to close it before we've connected? 
    // It should probably be up above...
    pool.end() 

}

应用程式

var connectToDb = require('./DataBase/ConnectToDb');
connectToDb((err, result) => {
    // This is a callback!
    if(err) console.log(err)
    else console.log(result)
})

用谷歌搜索： node.js回调模式