create-blog-post-with-tags.js

const { tags, ...blogPost } = {
  "title": "My first blog post",
  "body": "...",
  "tags": [
    { "text": "sequelize" },
    { "text": "feathersjs" },
    { "text": "many-to-many" }
   ]
};

const newPost = db.create('blog_posts', blogPost);
const newTags = db.createMany('tags', tags);
const blogPostTags = newTags.map(tag => {
  return { 
    tag_id: tag.id, 
    blog_post_id: newPost.id 
  };
});

db.createMany('blog_post_tags', blogPostTags);