Node.js - Using 'async' and 'await' with sequelize ORM

Question

I've been trying to find out how to make sequelize work with 'async' and 'await'. The best information I could find on that topic was an answer in this thread: Node.js 7 how to use sequelize transaction with async / await?

But I can't quite make it work in my project. I've been cutting out parts of code to make it simpler so I can work out what exactly is not right and ended up with something like this:

const Sequelize     =   require('sequelize');
const sequelize = new Sequelize('zas', 'zas', 'saz123', 
{
    host: 'someHost',
    dialect: 'mysql',

}
);
//test
let transaction;    
var SimpleInspectionModel   = require('../models/simpleInspectionModel.js')(sequelize, { dataTypes: Sequelize.DataTypes } );

try {
  // get transaction
  transaction = await sequelize.transaction();

  // step 2
  await SimpleInspectionModel.find({}, {transaction});

  // commit
  await transaction.commit();

} catch (err) {
  // Rollback transaction if any errors were encountered
  await transaction.rollback();
}

Whenever run, this code will output this kind of error :

transaction = await sequelize.transaction(); ^^^^^

SyntaxError: await is only valid in async function

at createScript (vm.js:80:10) at Object.runInThisContext (vm.js:139:10) at Module._compile (module.js:616:28) at Object.Module._extensions..js (module.js:663:10) at Module.load (module.js:565:32) at tryModuleLoad (module.js:505:12) at Function.Module._load (module.js:497:3) at Function.Module.runMain (module.js:693:10) at startup (bootstrap_node.js:191:16) at bootstrap_node.js:612:3

Project dependencies in package.json:

"body-parser": "^1.18.3" "express": "^4.16.3", "express-session": "^1.15.6", "file-system": "^2.2.2", "mysql2": "^1.5.3", "sequelize": "^4.37.10"

Node v8.11.3

Solution

You can only use await inside an async function, not at the top level. There's a proposal to support top-level await, but that is not currently supported in JS. Do this instead:

let transaction;
var SimpleInspectionModel = require('../models/simpleInspectionModel.js')(sequelize, { dataTypes: Sequelize.DataTypes } );

run().catch(error => console.log(error.stack));

async function run() {
  try {
    // get transaction
    transaction = await sequelize.transaction();

    // step 2
    await SimpleInspectionModel.find({}, {transaction});

    // commit
    await transaction.commit();

  } catch (err) {
    // Rollback transaction if any errors were encountered
    await transaction.rollback();
  }
}

Sequelize transactions support promises, so you should be able to use sequelize with async/await. I don't really know much about Sequelize but I wrote a blog post on using async/await with Mongoose, which is a similar tool for MongoDB, might be helpful to read.

Comments

[Ben Fortune]

The error message is telling you exactly what's wrong, you can only use await inside an async function block.

[Agash Thamo.]

@BenFortune is right. You have to declare the method or function the code block of yours is in it as async or wrap the code that uses await inside a self-invoking async function using (async function(){ … your code goes here … }) edit: or wrap it in a an actual function and call it

[Stormbytes]

The Sequelize docs explicitly say to use 'await' and there's no mention at all of using transactions. Bad info I guess.