jQuery.validator.addMethod中的.post始终返回false [英] .post inside jQuery.validator.addMethod always returns false

问题描述

我对jQuery和javascript编程非常陌生.我下面有一个程序可以检查是否使用了用户名.目前，PHP脚本始终返回

I am very new to jQuery and javascript programming. I have a program below that checks whether username is taken or not. For now, the PHP script always returns

  if(isset($_POST["username"]) )//&& isset($_POST["checking"]))
    {
        $xml="<register><message>Available</message></register>";
        echo $xml;
    }

登录功能有效，但用户名检查无效.有任何想法吗? 这是我所有的代码:

Login function works, but username checking doesn't. Any ideas? Here is all of my code:

$(document).ready(function() {
jQuery.validator.addMethod("checkAvailability",function(value,element){
    $.post( "login.php" , {username:"test", checking:"yes"}, function(xml){
        if($("message", xml).text() == "Available") return true;
        else return false;
    });
},"Sorry, this user name is not available");
$("#loginForm").validate({
    rules:  {
        username: {
            required: true,
            minlength: 4,
            checkAvailability: true
        },
        password:{
            required: true,
            minlength: 5
        }
    },
    messages: {
        username:{
            required: "You need to enter a username." ,
            minlength: jQuery.format("Your username should be at least {0} characters long.")
        }
    },
    highlight: function(element, errorClass) {
                $(element).fadeOut("fast",function() {
                $(element).fadeIn("slow");
                })
    },
    success: function(x){
        x.text("OK!")
    },
    submitHandler: function(form){send()}
});
function send(){
    $("#message").hide("fast");
    $.post( "login.php" , {username:$("#username").val(), password:$("#password").val()}, function(xml){
        $("#message").html( $("message", xml).text() );
        if($("message", xml).text() == "You are successfully logged in.")
        {
            $("#message").css({ "color": "green" });
            $("#message").fadeIn("slow", function(){location.reload(true);});
        }
        else
        {
            $("#message").css({ "color": "red" });
            $("#message").fadeIn("slow");
        }
    });
}
$("#newUser").click(function(){

    return false;
});

});

推荐答案

您需要使用 $.post() ，它是 $.ajax() ，因此您可以设置选项为false，如下所示:

You need to use the expanded form of $.post() which is $.ajax() so you can set the async option to false, like this:

jQuery.validator.addMethod("checkAvailability",function(value,element){
    $.ajax({
      url: "login.php",
      type: 'POST',
      async: false,
      data: {username:"test", checking:"yes"},
      success: function(xml) {
        return $("message", xml).text() == "Available";
      }
    });
},"Sorry, this user name is not available");

当前，您的用于分析响应的success函数在验证完成后之后发生，因为这是异步操作.因此，当前，在使用返回值时，它不会返回任何内容，并且undefined〜= false，这就是为什么它总是显示为false的原因.通过将async设置为false，可以让代码按顺序执行而无需回调，因此实际上使用了上面示例中的return.

Currently your success function that analyzes the response happens after the validation finishes, because it's an asynchronous operation. So currently, it's not returning anything at the time the return value is used, and undefined ~= false, which is why it always appears false. By setting async to false, you're letting the code execute in order without the callback, so the return in the example above is actually used.

如果可以调整页面的返回结构，另一种选择是使用验证插件的内置

Another alternative, if you can adjust your page's return structure is to use the validation plugin's built-in remote option, which is for just this sort of thing :)

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