Question

the jquery

$(document).on('click', '#fun', function (e) {
    var $this = $(this);
    var request = $.ajax({
      url: "example.php",
      type: "POST",
      data: {bla: blabla},
      dataType: "html"
    });

    request.done(function(msg) {
        if(msg)
        {
            $this.addClass("btn btn-info btn-small marked");
            $("#isMarked", $this).val(msg)
        }
        else if(!msg)
        {
            $this.addClass("btn btn-small unmarked");
            $("#isMarked", $this).val(msg);
        }
    });

and the button

<a id='fun' class='btn btn-info btn-small marked' href='#'>fun</a>

example.php will return a value either 0 or 1 (indicate true or false)
so the msg will be 0 or 1

the addClass in else if(!msg) can’t works. I can’t find the problem. any idea?

Answer 1

msg will be a string so you are comparing a string in the if so it should always be true since a string is a truthy value.

​var str1 = "0";
var str2 = "1";

var x = str1 ? "true" : "false";
var y = str2 ? "true" : "false";

​alert(x+"\n"+y);​​​​