Access array values after knex SELECT

Question

I have the following code snippet in an Electron app to retrieve a given column in a sqlite3 database:

database.js

var database = require("knex")({
    client: "sqlite3",
    connection: {
        filename: path.join(__dirname, 'db/food.db')
    },
  useNullAsDefault: true
});

const fetchItems = (colName) => {
  let itemList = database.select(colName).from('food')
  itemList.then(() => {
    // console.log(itemList);
    return itemList;
  }).catch((err) => {
    console.log(err)
    return [];
  })
}

When I try accessing the array itemList, I got a message undefined. When I try printing it out to console, it shows lengthy info of the database object as following:

Builder [object] {
  client: Client_SQLite3 {
    config: { client: 'sqlite3', connection: [Object], useNullAsDefault: true },
    logger: Logger {
      _inspectionDepth: 5,
      _enableColors: true,
      _debug: undefined,
      _warn: undefined,
      _error: undefined,
      _deprecate: undefined
    },
    connectionSettings: {
      filename: '/home/.../db/food.db'
    },
    connectionConfigExpirationChecker: null,
    driver: {
      Database: [Function: Database],
      Statement: [Function: Statement],
      Backup: [Function: Backup],
      OPEN_READONLY: 1,
...

How do I go about accessing the array (i.e. column) of values? Thanks.

Update: here is how I call this fetchItems function in main.js.

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

ipcMain.on("showItemsButtonClicked", function () {
        let itemList = database.fetchItems('food_name');

        itemList.then(() => {
            mainWindow.webContents.send("itemsRetrieved", itemList);
        })
        console.log(itemList);
    });

Lavish Jain · Accepted Answer · 2020-11-27 21:50:52Z

1

I think you are using the wrong syntax.

  const fetchItems = (colName) => {
  let itemList = database.select(colName).from('food').then((res) => {
    // console.log(res);
    return res;
  }).catch((err) => {
    console.log(err)
    return [];
  })
 return itemList
}

Using async await:

const fetchItems = async(colName) => {
  try {
    let itemList = await database.select(colName).from('food')
    return itemList
  } catch(err) {
    console.log(err)
    return [];
  }
}

answered Nov 27, 2020 at 21:50

Lavish Jain

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2 Comments

Tristan Tran Over a year ago

Thanks. I added more details in my question. I tried both of your suggestions. First sugestion: i can print to console the res correctly, but res is not returned to fetchItems function (hence, main.js does not receive it). Second: I got Javascript error in main process. Erros: failed to serialize arguments....

Tristan Tran Over a year ago

Ok, I tried again and the async await solution works for me (need to modify the main.js code to receive a promise). Thanks. Closing this.

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