【Rails】【非同期通信】create.js.hamlがうまく機能しない=>create.js.erbにすることで解決（したように見えた初歩的ミス）

class User < ApplicationRecord
# (中略)
  has_many :likes
  has_many :items
end

class Item < ApplicationRecord
# (中略)
  has_many :likes

  def liked?(user)
    likes.where(user_id: user.id).exists?
  end
end

class Like < ApplicationRecord
  belongs_to :user
  belongs_to :item
  validates :user_id, presence: true
  validates :item_id, presence: true
  validates_uniqueness_of :item_id, scope: :user_id
end

class ItemsController < ApplicationController
# (中略)
  def show
    @item = Item.find(params[:id])
    @likes_count = @item.likes.length
  end
end

class LikesController < ApplicationController
  before_action :item_setting

  def create
    @like = current_user.likes.new(item_id: params[:item_id])
    if @like.save
      return_likes_count
    else
      return_error
    end
  end

  def destroy
    if @like = current_user.likes.find_by(item_id: params[:item_id])
      if @like.destroy
        return_likes_count
      else
        return_error
      end
    else
      return_error
    end
  end

  private

  def item_setting
    @item = Item.find(params[:item_id])
  end

  def return_likes_count
    @likes_count = @item.likes.length
  end

  def return_error
    @likes_count = "err"
  end
end

// (前略)
#likes
  = render partial: "likes", locals: {item: @item}
// (後略)

// このファイル内の「@item」は「item」とした方が正確な書き方かもしれません
- if user_signed_in? && @item.liked?(current_user)
  = link_to item_likes_path(@item.id), method: :delete, remote: true do
    %li.items-tag__left--good{id: "good_btn_liked"}
      = icon('far', 'heart')
      %span いいね!
      %span#likes_count
        = @likes_count
- elsif user_signed_in?
  = link_to item_likes_path(@item.id), method: :post, remote: true do
    %li.items-tag__left--good{id: "good_btn"}
      = icon('far', 'heart')
      %span いいね!
      %span#likes_count
        = @likes_count
- else
  %li.items-tag__left--good{id: "#{'good_btn' if user_signed_in?}"+"#{'_liked' if user_signed_in? && current_user.likes.exists?(item_id: @item.id)}"}
    = icon('far', 'heart')
    %span いいね!
    %span#likes_count
      = @likes_count

// これらのファイルがエラーの原因でした
$('#likes').html(“#{j(render partial: "items/likes", locals: { item: @item })}");

Uncaught SyntaxError: Invalid or unexpected token                  VM3330:1 
    at processResponse (rails-ujs.self-43e81c501e7e36871a34b4b950451cc7cb047af4e846ec742539e64724582452.js?body=1:273)
    at rails-ujs.self-43e81c501e7e36871a34b4b950451cc7cb047af4e846ec742539e64724582452.js?body=1:201
    at XMLHttpRequest.xhr.onreadystatechange (rails-ujs.self-43e81c501e7e36871a34b4b950451cc7cb047af4e846ec742539e64724582452.js?body=1:256)

$('#likes').html(“<a data-remote=\"true\" rel=\"nofollow\" data-method=\"delete\" href=\"/items/5/likes\"><li class=\'items-tag__left--good\' id=\'good_btn_liked\'>\n<i class=\"far fa-heart\"><\/i>\n<span>いいね!<\/span>\n<span id=\'likes_count\'>\n3\n<\/span>\n<\/li>\n<\/a>");
                 ^ よく見るとここの記号がダブルクォート(")じゃない。なにこれ？

<%# ファイル形式をhamlからerbに変更しました %>
$('#likes').html("<%= j(render partial: 'items/likes', locals: {item: @item}) %>");

$('#likes').html("<a data-remote=\"true\" rel=\"nofollow\" data-method=\"delete\" href=\"/items/5/likes\"><li class=\'items-tag__left--good\' id=\'good_btn_liked\'>\n<i class=\"far fa-heart\"><\/i>\n<span>いいね!<\/span>\n<span id=\'likes_count\'>\n3\n<\/span>\n<\/li>\n<\/a>");