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JavaScript Using SQL ORMs with Node.js Getting Started with Sequelize Test the Database

Posted by Zimri Leijen
Zimri Leijen
11,835 Points

Avoid repeating multiple `Movie.create()` instructions

I can see if you'd want to add lots of movies you'd get a lot of repeated code.

Doing it this way you don't need to repeat any code and you'll get the exact same results. 

(async () => {
    await sequelize.sync({ force: true });
    try{
        const movieCreations = ['Toy Story', 'The Incredibles'].map( title => Movie.create({ title }))
        await Promise.all(movieCreations);

    } catch(error){
        console.error('Error connecting to the database: ', error)
    };
}) ();

Edit:

after the end of the course, I ended up with something like this:

(async () => {
    await db.sequelize.sync({ force: true });
    try {
        const movies = [
            {title: 'Toy Story', releaseDate: '1995-11-22', runtime: 81, isAvailableOnVHS: true},
            {title: 'The Incredibles', runtime: 115, releaseDate: '2004-04-14', isAvailableOnVHS: true},
            {releaseDate: '1998-01-15', title: 'Titanic', runtime: 195, isAvailableOnVHS: true},
        ].map( ({ title, runtime, releaseDate, isAvailableOnVHS } ) => Movie.create({
            title,
            runtime,
            releaseDate,
            isAvailableOnVHS
        }));
        const persons = [
            {firstName: 'Leonardo', lastName: 'diCaprio'},
        ].map( ({ firstName, lastName }) => Person.create({
            firstName,
            lastName
        }));
        await Promise.all([...movies, ...persons]);
    } catch(error) {
        if(error.name === 'SequelizeValidationError') {
            const errors = error.errors.map(err => err.message);
            console.error('Validation errors:', errors);
        } else {
            throw error;
        }        
    };
}) ();
Seokhyun Wie
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.a{fill-rule:evenodd;}techdegree seal-36
Seokhyun Wie
Full Stack JavaScript Techdegree Graduate 21,606 Points
Seokhyun Wie
.a{fill-rule:evenodd;}techdegree seal-36
Seokhyun Wie
Full Stack JavaScript Techdegree Graduate 21,606 Points

I didn't use ... notation in Promise.all and it still works perfect. Can anyone explain what are the possible errors or benefits etc. using ... notation particularly in this case? Thanks in advance.

Jamie Gobeille
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Jamie Gobeille
Full Stack JavaScript Techdegree Graduate 19,573 Points
Jamie Gobeille
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Jamie Gobeille
Full Stack JavaScript Techdegree Graduate 19,573 Points

That was such a good idea to do it that way! I used this pattern for my project as well!

I separated my arrays and create Functions so it was easier to read(for me at least).

//reusable Function
const mapFunction = (array, model) => {
  array.map(
    //maps through each object in the array, then destructures it
    (object) => model.create({ ...object })
  );
};

(async () => {

  //Sync all tables
  await db.sequelize.sync({ force: true });
  try {
    //Array of movie data
    const movies = [
      {
        title: "Toy Story",
        runtime: 81,
        releaseDate: "1995-11-22",
        isAvailableOnVHS: true,
      },
      {
        title: "The Incredibles",
        runtime: 115,
        releaseDate: "2004-04-14",
        isAvailableOnVHS: true,
      },
    ];

    const people = [
      { firstName: "Tom", lastName: "Hanks" },
      { firstName: "Tim", lastName: "Allen" },
      { firstName: "Brad", lastName: "Bird" },
      { firstName: "Holly", lastName: "Hunter" },
    ];
    // Instance of the Movie class represents a database row
    //create movies
    const movieCreations = mapFunction(movies, Movie);
    //create Person
    const peopleCreations = mapFunction(people, Person);

    await Promise.all([movieCreations, peopleCreations]);

  } catch (error) {
    if (error.name === "SequelizeValidationError") {
      const errors = error.errors.map((err) => err.message);
      console.error("Validation errors: ", errors);
    } else {
      throw error;
    }
  }
})();

2 Answers

Brian Wright
Brian Wright
6,770 Points
Brian Wright
Brian Wright
6,770 Points

Sequelize has a Model function bulkCreate(). This works in the same way as create but you pass an array of movie objects instead of a single movie object.