一个新的问题，从这个线程出现了： jQuery的表单验证从来没有让Ajax调用，在从Ajax请求返回的数据是准确的，但它总是失败的一个比较。这是code，使Ajax请求：

A new problem emerged from this thread: jquery form validator never makes ajax call, in that the data returned from the ajax request is accurate, but it always fails on a comparison. This is the code that makes the ajax request:

var pass_form = $('#pass_form');
pass_form.submit( valid_pass_sett );

function valid_pass_sett() {
    //remove old errors - snipped
    pass_old = $('input[name=pass_old]').val();
    pass_new = $('input[name=pass_new]').val();
    pass_confirm_new = $('input[name=pass_confirm_new]').val();

    if (pass_old === "") {
        //display error on form - snipped
        return false;
    } else if (pass_new === "") {
        //display error on form - snipped
        return false;
    } else if (pass_new != pass_confirm_new) {
        //display error on form - snipped
        return false;
    } else if (pass_new.length < 8) {
        //display error on form - snipped
        return false;
    } else {
        $.post("http://www.example.com/ajax/validate.php",{ // async validation
            type: 'valid_old_change_pass', 
            pass_old: pass_old,
            pass_new: pass_new
        }, valid_pass_combo_callback);
        alert('after the ajax call...');
    }
    return false;  // cancel form submission
}

这是该请求被提交到code：

this is the code that the request is submitted to:

$username = $_SESSION['username'];
$pass_old = $_POST['pass_old'];
$pass_new = $_POST['pass_new'];
if (empty($pass_old) || empty($pass_new)) {
    echo "invalid";
} else if (!User::valid_user_pass($username, $pass_old)) {
    echo "invalid_old";
} else if (!Sanitize::is_legal_password($pass_new)) {
    echo "invalid_new";
} else {
    echo "valid";
}

和这是回调函数处理它;回调函数是一个地方比较总是失败。

and this is the callback function that processes it; the callback function is the one where the comparison always fails.

function valid_pass_combo_callback( data ) {

//breakpoint is set here
    if (data == 'valid') {
        //only if the form is valid!
        pass_form[0].unbind('submit').submit();
    }
    else if (data == "invalid_old") {
        //display error on form - snipped
    }
    else if (data == "invalid_new") {
        //display error on form - snipped
    }
    else {
        //it always jumps to here..., even though data *is* the correct value
    }
}

我调试这个code和validate.php将返回invalid_old这是正确的（根据测试数据，我进入）。因此，数据是invalid_old根据Firebug的存储;然而，code的总是的跳转到最后else语句。为什么总是比较失败？

I debugged this code, and validate.php is returning "invalid_old" which is correct (based on the test data I'm entering). So, data is storing "invalid_old" according to Firebug; however, the code always jumps down to the last else statement. Why is the comparison always failing?

推荐答案

正如在注释中，加入jQuery的修剪功能解决了这一问题，如下所示：

As stated in the comment, adding JQuery's trim function fixed the problem, as shown:

function valid_pass_combo_callback( data ) {
    trimmed_data = $.trim(data);
    if (trimmed_data == 'valid') {
        //only if the form is valid!
        pass_form[0].unbind('submit').submit();
    }
    else if (trimmed_data == "invalid_old") {
        //display error on form - snipped
    }
    else if (trimmed_data == "invalid_new") {
        //display error on form - snipped
    }
    else {
        //it always jumps to here..., even though data *is* the correct value
    }
}