ES6类方法在实例中不存在

Question

I am updating my old node.js project to include ES6 features in order to eventually migrate to typescript, but I can't get this class to work. I have defined a class in a separate file:

class Database {

constructor(connectionPool) {
    this._connectionPool = connectionPool;
}

_getConnection () {
    console.log("getting connection");
    return new Promise((resolve, reject) => {
        this._connectionPool.getConnection((err, connection) => {
            if (err) {
                reject(err);
                console.log("connection rejected");
            } else {
                console.log("connection resolved");
                resolve(connection);
            }
        });
    });
}
}
module.exports = Database;

I am then importing this class into another file and trying to create a Database instance:

const mysql = require('mysql');
const Database = require('./database');

module.exports = databaseInitializer;

function databaseInitializer(config) {

    const pool = mysql.createPool(config);
    const db = new Database(pool);
    console.log(Database.toString());
    console.log(db.__proto__);
    return db;
}

Finally, i am using above function to get the database instance:

const database = require('./models/databaseInitializer')(mysqlConfig);
console.log(database);

Now, my database instance has a _connectionPool property, but no prototype and more importantly, no _getConnection property. What am I missing?

Thanks and best regards

Answer 1

_getConnection property belongs to the prototype of database and hence this property is the non-enumerable property of database .

You can access this property by doing

console.log(database._getConnection) //should show the function