javascript - 在注册过程中检查重复 key (Django、JS、Ajax)

Question

我有一个名为 onsubmit 的 JavaScript 函数:

function formCheck(){
    return usernameCheck() && passwordCheck();
}

passwordCheck() 工作正常并按预期返回内容，但由于某种原因 usernameCheck() 出现问题:

function usernameCheck(){ //returns true if username is free
var ajaxHeaders = {}; //create header object
ajaxHeaders["X-CSRFToken"] = getCookie('csrftoken'); //add csrftoken from cookies for authentication server-side
$.ajax({
    type:'POST',
    url:"http://omnicloud.me/signup", 
  data:{username: $("#username").value}, 
  success:function(response){
    if(response=="true"){
       $('#passAlert').innerHTML("Sorry, that username is already taken") 
       //passalert is where all of the errors (username taken, invalid password) show up
    }
    },
headers: ajaxHeaders //settings for ajax request
});

return !($('#passAlert').value == "Sorry, that username is already taken")
}

在后端:

def signup(request):
if request.method == 'GET':
    return render_to_response('signup.html', context_instance=RequestContext(request))
elif request.is_ajax(): 
#query db for user with username provided via ajax, return if it exists
    try:    
        user = User.objects.get(username=request.POST.get("username")) 
    except User.DoesNotExist:
        return HttpResponse("false",context_instance=RequestContext(request))
    else:
        return HttpResponse("true", context_instance=RequestContext(request))

Answer 1

Ajax 中的 A 代表异步。您提供的 success 函数不会立即执行，而是在浏览器从服务器获取响应后调用，这将在您从 usernameCheck() 返回后> 功能。

您无法使用返回值进行此检查，您必须使用回调。