jquery ajax在没有firebug断点的情况下不工作 [英] jquery ajax dont work without firebug break point

问题描述

我使用以下方法来调用php：

I am using following method to call the php:

function validateEmaiAjax(email){
    val = null;
    $("#warning").load("https://localhost/Continental%20Tourism/register_ajax.php",{email: email}, function(rspns, stat, xml){
        val = rspns;
    });

    if(val == ".")
        return true;
    else {
        return false;
    }
}

我的PHP代码是：

<?php
    $dbc = mysqli_connect("localhost","root","pass","continental_tourism") OR die(mysqli_connect_error());

    $email = $_REQUEST['email'];

    $query = "SELECT email FROM customer_info WHERE email = '$email' ";

    $r = mysqli_query($dbc, $query) OR die(mysqli_error($dbc));

    if(mysqli_num_rows($r) > 0)
        echo "Email address exists!";
    else
        echo ".";   
?>

基本上这会检查数据库，如果有电子邮件显示电子邮件地址存在！如果不是我想返回true （所以我回显。并进行比较）。奇怪的是，如果我在附近使用firebug设置断点if if（val ==。）程序正常工作并返回true。如果我删除该断点函数总是返回false。我不明白为什么会这样。请帮忙！谢谢。

Basically this do check the database and if email exists shows "Email address exists!" if not I want to return true(so I echo "." and compare it). The weird thing is if i put a break point using firebug near if(val == ".") program works correctly and returns true. If I remove that break point function always return false. I cant understand why this happens. Please help! Thanks.

推荐答案

您遇到此问题的原因是您执行了异步请求。这意味着在从服务器收到响应之前，将达到 if（rspns ==。），结果将始终为 false 。

The reason you have this problem is because you have performed an asynchronous request. This means that the if(rspns == ".") will be reached before the response has been received from the server, and the result will always be false.

为了在函数中包装此代码，返回一个布尔值，不需要回调函数（阻塞过程）您将需要使用同步请求：

In order to wrap this code in a function the returns a boolean and does not require a callback function (a blocking procedure) you will need to use a synchronous request:

function validateEmaiAjax(email) {

  // This is the correct way to initialise a variable with no value in a function
  var val;

  // Make a synchronous HTTP request
  $.ajax({
    url: "https://localhost/Continental%20Tourism/register_ajax.php",
    async: false,
    data: {
      email: email
    },
    success: function(response) {
      // Update the DOM and send response data back to parent function
      $("#warning").html(response);
      val = response;
    }
  });

  // Now this will work
  if(val == ".") {
    return true;
  } else {
    $("#warning").show();
    return false;
  }

}

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