轮询和长轮询

轮询：轮询就是第隔N秒访问一次服务器
长轮询：访问一次服务器时间比较长，如20秒，并且如果有数据返回则立马结束

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# urls urlpatterns = [     path('admin/', admin.site.urls),     path('index/', views.index),     path('get_json/', views.get_json),     path('put_data/', views.put_data), ]   # views from django.shortcuts import render from django.http import HttpResponse import json from queue import Queue, Empty   que = Queue()     # Create your views here. def index(request):     return render(request, 'index.html')     def get_json(request):     # 轮询     # data = {'name': 'Alex', 'age': 33}     # return HttpResponse(json.dumps(data))     # 轮询结束     # 长轮询开始     # 队列模拟长轮询，队列等待10秒     response = {'status': True, 'data': None}     try:         val = que.get(timeout=10)         response['data'] = val     except Empty as e:         response['status'] = False     return HttpResponse(json.dumps(response))     # 长轮询结束     def put_data(request):     que.put('随便放一此数据')     return HttpResponse('已经发送数据') # HTML和JS                 Title           空内容 # JS开始         // 轮询开始     /*    $(function () {             // 轮询的关键             setInterval(func, 2000)         });         function func() {             $.ajax({                 url:'/get_json/',                 type:'post',                 success:function (data) {                     data = JSON.parse(data);                     console.log(data);                 }             })         }*/     // 轮询结束     // 长轮询开始     $(function () {         func()     }); function func() {     $.ajax({         url: '/get_json/',         type: 'post',         success: function (data) {             data = JSON.parse(data);             if (data.status){                 location.href='http://www.baidu.com/'             }             // 自己调用自己是长轮询的关键             func()         }     }) } // 长轮询结束   JS结束