Updated process for making unique slug in Learn Node course by Wes Bos

slug.js

storeSchema.pre('save', async function(next) {
  if (!this.isModified('name')) {
    next(); // skip it
    return; // stop this function from running
  }

  var _slug = slug(this.name);
  this.slug = _slug;
  // find other stores that have a slug of wes, wes-1, wes-2
  const slugRegEx = new RegExp(`^(${_slug})((-[0-9]*$)?)$`, 'i');
  const storesWithSlug = await this.constructor.find({ slug: slugRegEx });

  if (storesWithSlug.length) {
    var idx = 1;
    while(storesWithSlug.find((store)=> {return store.slug === this.slug})) {
      this.slug = `${_slug}-${storesWithSlug.length + idx++}`;
    }
  }
  next();
  // TODO make more resiliant so slugs are unique
});