Javascript 使用上一个下拉列表的结果填充下拉列表

我有一个Rails数据库，里面有学校和专业。一旦用户选择了他的学校，我想用对应学校的专业来填充专业下拉列表。目前，我有两个工作下拉列表，但正如您所看到的，它们只选择所有值。我需要Json/Ajax/JavaScript吗？如果需要，我如何实现它

<div class="field">
  <%= f.label :school_id %><br>
  <%= f.collection_select :school_id, School.order(:name),:id,:name, include_blank: false %>
</div>
<div class="field">
  <%= f.label :major_id %><br>
  <%= f.collection_select :major_id, Major.order(:name),:id,:name, include_blank: false %>
</div>

编辑

---

当前的解决方案是对每个下拉选择使用异步请求。假设你有一小部分选择（假设这将帮助你成为一个美丽的人。祝你有美好的一天！干得好！在这里工作得很好：）

<!-- app/views/courses/_form.html.erb -->
<div class="field">
  <%= f.label :school_id %><br>
  <%= f.collection_select :school_id, School.order(:name),:id,:name, {include_blank: false},{:id=>'school_id_select'} %>
</div>
<div class="field">
  <%= f.label :major_id %><br>
  <%= f.collection_select :major_id, [],:id,:name, {include_blank: false},{:id=>'major_id_select'} %>
</div>

#config/routes.rb
Rails.application.routes.draw do
  #...
  get 'majors/find_majors_given_school_id'
  #...
end

#app/controllers/majors_controller.rb
#custom action for AJAX/JSON calls. Note this can be done multiple ways
def find_majors_given_school_id
   school_id = params[:school_id]#utilizes the url to extract school_id ".../find_majors_given_school_id?school_id=123123"
   puts "THIS IS MY SCHOOL ID :: #{school_id}"#view this in teminal
    
   majors = Major.search_for_school_id(school_id).as_json#query the model for the data and convert it to a hash using as_json
   puts "THESE ARE MY MAJORS IN A HASH :: #{majors}"
   respond_to do |format|
        format.json { 
            render json: majors
        } 
   end
end

#app/models/major.rb
class Major < ActiveRecord::Base
    has_many :courses, dependent: :destroy
    belongs_to :school, :foreign_key => "school_id"

    def self.search_for_school_id(id)
        where("school_id = ?",id)        
    end
    #...
end