more sequelize stuff

rootfs_overlay/lkmc/nodejs/sequelize/association_many_to_many.js

@@ -0,0 +1,132 @@
+#!/usr/bin/env node
+
+// https://stackoverflow.com/questions/22958683/how-to-implement-many-to-many-association-in-sequelize/67973948#67973948
+
+const assert = require('assert');
+const path = require('path');
+
+const { Sequelize, DataTypes } = require('sequelize');
+
+const sequelize = new Sequelize({
+  dialect: 'sqlite',
+  storage: 'tmp.' + path.basename(__filename) + '.sqlite',
+});
+
+(async () => {
+
+// Create the tables.
+const User = sequelize.define('User', {
+  name: { type: DataTypes.STRING },
+}, {});
+const Post = sequelize.define('Post', {
+  body: { type: DataTypes.STRING },
+}, {});
+// UserLikesPost is the name of the relation table.
+// Sequelize creates it automatically for us.
+// On SQLite that table looks like this:
+// CREATE TABLE `UserLikesPost` (
+//   `createdAt` DATETIME NOT NULL,
+//   `updatedAt` DATETIME NOT NULL,
+//   `UserId` INTEGER NOT NULL REFERENCES `Users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
+//   `PostId` INTEGER NOT NULL REFERENCES `Posts` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
+//   PRIMARY KEY (`UserId`, `PostId`)
+// );
+User.belongsToMany(Post, {through: 'UserLikesPost'});
+Post.belongsToMany(User, {through: 'UserLikesPost'});
+await sequelize.sync({force: true});
+
+// Create some users and likes.
+
+const user0 = await User.create({name: 'user0'})
+const user1 = await User.create({name: 'user1'})
+const user2 = await User.create({name: 'user2'})
+
+const post0 = await Post.create({body: 'post0'});
+const post1 = await Post.create({body: 'post1'});
+const post2 = await Post.create({body: 'post2'});
+
+// Autogenerated add* methods
+
+// Make user0 like post0
+await user0.addPost(post0)
+// Make user0 and user2 like post1
+await post1.addUsers([user0, user2])
+
+// Autogenerated get* methods
+
+// Get likes by a user.
+
+const user0Likes = await user0.getPosts({order: [['body', 'ASC']]})
+assert(user0Likes[0].body === 'post0');
+assert(user0Likes[1].body === 'post1');
+assert(user0Likes.length === 2);
+
+const user1Likes = await user1.getPosts({order: [['body', 'ASC']]})
+assert(user1Likes.length === 0);
+
+const user2Likes = await user2.getPosts({order: [['body', 'ASC']]})
+assert(user2Likes[0].body === 'post1');
+assert(user2Likes.length === 1);
+
+// Get users that liked a given likes.
+
+const post0Likers = await post0.getUsers({order: [['name', 'ASC']]})
+assert(post0Likers[0].name === 'user0');
+assert(post0Likers.length === 1);
+
+const post1Likers = await post1.getUsers({order: [['name', 'ASC']]})
+assert(post1Likers[0].name === 'user0');
+assert(post1Likers[1].name === 'user2');
+assert(post1Likers.length === 2);
+
+const post2Likers = await post2.getUsers({order: [['name', 'ASC']]})
+assert(post1Likers[0].name === 'user0');
+assert(post1Likers[1].name === 'user2');
+assert(post1Likers.length === 2);
+
+// Autogenerated has* methods
+
+// Check if user likes post.
+assert( await user0.hasPost(post0))
+assert( await user0.hasPost(post1))
+assert(!await user0.hasPost(post2))
+
+// Check if post is liked by user.
+assert( await post0.hasUser(user0))
+assert(!await post0.hasUser(user1))
+assert(!await post0.hasUser(user2))
+
+// AND of multiple has checks at once.
+assert( await user0.hasPosts([post0, post1]))
+assert(!await user0.hasPosts([post0, post1, post2]))
+
+// Autogenerated count* methods
+assert(await user0.countPosts() === 2)
+assert(await post0.countUsers() === 1)
+
+// Autogenerated remove* method
+
+// user0 doesn't like post0 anymore.
+await user0.removePost(post0)
+// user0 and user 2 don't like post1 anymore.
+await post1.removeUsers([user0, user2])
+// Check that no-one likes anything anymore.
+assert(await user0.countPosts() === 0)
+assert(await post0.countUsers() === 0)
+
+// Autogenerated create* method
+// Create a new post and automatically make user0 like it.
+const post3 = await user0.createPost({'body': 'post3'})
+assert(await user0.hasPost(post3))
+assert(await post3.hasUser(user0))
+
+// Autogenerated set* method
+// Make user0 like exactly these posts. Unlike anything else.
+await user0.setPosts([post1, post2])
+assert(!await user0.hasPost(post0))
+assert( await user0.hasPost(post1))
+assert( await user0.hasPost(post2))
+assert(!await user0.hasPost(post3))
+
+await sequelize.close();
+})();