jQuery，否则，如果不起作用

Question

I'm sending data to my database using .ajax. I've got two fields. I'd like to check if either are empty and if so display an error. The first if works fine. That message display, but the else if doesn't display. What could be my problem? I'm not too familiar with javascript and iquery.

$.ajax({
    type: "POST",
    url: "submit.php",
    data: data,
    cache: false,
     beforeSend: function() {
        if (!$.trim($("#cat").val())) {
            $(".fb-error").css( "display", "block" );
            $(".fb-error").html("<p>the cat field is empty</p>");
            xhr.abort();
        }

        else if (!$.trim($("#box").val())) {
            $(".fb-error").css( "display", "block" );
            $(".fb-error").html("<p>the box field is empty</p>");
            xhr.abort();
        }
    },
    success: function(html){
        $('textarea#box').val('');
        $("#box-wrap").prepend(html);
    }
});

Answer 1

You can't use else if you want to check both conditions.

var error = '';

if (!$.trim($("#cat").val())) {
        error = "<p>the cat field is empty</p>";
}

if (!$.trim($("#box").val())) {
        error += "<p>the box field is empty</p>";
}

if (error) {
        $(".fb-error").html(error);
        $(".fb-error").css( "display", "block" );
        xhr.abort();
}

In second if you have to append new html, to prevent overwriting already added message.

Answer 2

Use separate if statements for each condition; else if only runs if the first if fails. Use a variable to accumulate the messages.

 beforeSend: function() {
    var msg = '';
    if (!$.trim($("#cat").val())) {
        $(".fb-error").css( "display", "block" );
        msg = "<p>the cat field is empty</p>";
        xhr.abort();
    }
    if (!$.trim($("#box").val())) {
        $(".fb-error").css( "display", "block" );
        msg += "<p>the box field is empty</p>";
        xhr.abort();
    }
    $(".fb-error").html(msg);
},

Answer 3

I'd put the errors in an array, and display them if it's not empty

var errors = [];
if (!$.trim($("#cat").val())) {
    errors.push("<p>the cat field is empty</p>");
}

if (!$.trim($("#box").val())) {
    errors.push("<p>the box field is empty</p>");
}

if(errors.length){
    $(".fb-error").css( "display", "block" ).html(errors.join(''));
    xhr.abort();
}

Answer 4

Consolidate:

var error = false;
if (!$.trim($("#cat").val())) {
        $(".fb-error").append("<p>the cat field is empty</p>");
        error = true;
}

if (!$.trim($("#box").val())) {
        $(".fb-error").append("<p>the box field is empty</p>");
        error = true;
}

if (error) {
        xhr.abort();
        $(".fb-error").css( "display", "block" );
}

Answer 5

To debug can you switch around #box and #cat?

You are using an else, so if #cat is empty, you will not see the message "the box field is empty". It will only show this message if #cat is not empty, and #box is.

change #box to something you know doesn't exist (and cannot exist). perhaps there is a value in it.

you could ouput the value of #cat and #box to the console to ensure that they are empty.

console.log("$.trim($("#cat").val()="+$.trim($("#cat").val()); console.log("$.trim($("#box").val()="+$.trim($("#box").val());