javascript - JSON or Jquery error: Uncaught TypeError: Cannot read property 'error' of null - Stack Overflow

admin管理员组

文章数量:1345733

I am trying to make an ajax call using the below jQuery.

But I can see in Chrome, i'm getting uncaught typeerror cannot read property 'error' of null. So this stops the preloader from going away. Any idea why it's doing this?

function appendTeam(){

$.ajax({

       url : _path + "/core/ajax.php",
       type : 'POST',
       data : { f: 'getTeam'},
       dataType : 'json',
       success :  function(data) {

        if(data.error){

            errorMessage('Error: ' + data.error, data.error, data.error);
            return false;

        }else{
            var count = 0;
            $.each(data.team, function(i, c){
                // check
                if(!$('#'+c)) return true;
                var element = $('#'+c);
                $('input[name="s'+i+'"]').val(element.attr('id'));
                $('.slot.'+(i+1)+'.ui-droppable').append(element);
                element.data('prevParent', $('.slot.'+(i+1)+'.ui-droppable'));
                count ++;

            });

            appendStatus(count);
            setTimeout(function(){
                $('#preloader').fadeOut('fast',function(){
                    $('#preloader').remove();
                    popUp('match');
                });
            }, 2000);


        }

    }
});
}

I am trying to make an ajax call using the below jQuery.

But I can see in Chrome, i'm getting uncaught typeerror cannot read property 'error' of null. So this stops the preloader from going away. Any idea why it's doing this?

function appendTeam(){

$.ajax({

       url : _path + "/core/ajax.php",
       type : 'POST',
       data : { f: 'getTeam'},
       dataType : 'json',
       success :  function(data) {

        if(data.error){

            errorMessage('Error: ' + data.error, data.error, data.error);
            return false;

        }else{
            var count = 0;
            $.each(data.team, function(i, c){
                // check
                if(!$('#'+c)) return true;
                var element = $('#'+c);
                $('input[name="s'+i+'"]').val(element.attr('id'));
                $('.slot.'+(i+1)+'.ui-droppable').append(element);
                element.data('prevParent', $('.slot.'+(i+1)+'.ui-droppable'));
                count ++;

            });

            appendStatus(count);
            setTimeout(function(){
                $('#preloader').fadeOut('fast',function(){
                    $('#preloader').remove();
                    popUp('match');
                });
            }, 2000);


        }

    }
});
}

• javascript
• jquery
• json

Share Improve this question Follow asked Oct 8, 2013 at 4:47 Dj IkeDj Ike 2511 gold badge11 silver badge77 bronze badges 2

• Can you add an example of the JSON that Ajax.php is rendering? – Jason Sperske Commented Oct 8, 2013 at 4:50
• 2 Also the success callbacks don't need/use return statements – Jason Sperske Commented Oct 8, 2013 at 4:52

Add a ment  | 

4 Answers 4

Sorted by: Reset to default 6

There is a mistake in your if operator:

if(data.error)...

You should check it like if(data && data.error)... so if the server returned you null instead of JSON object you won't try to access object's property error.

Also maybe you need to handle this case separately:

if(!data) {
    // handle empty response
} else if(data.error) {
    // handle error
} else {
    // process results
}

Test if data is not null before trying acces his error property

Probably the data object does not contains the property error or it is null;

so instead of this

if(data.error) {

you can check for it in a different way :

if(data && data.hasOwnProperty('error')) {

which is more fail-safe.

i think response is null try to see response in using firebug

本文标签： javascriptJSON or Jquery error Uncaught TypeError Cannot read property 39error39 of nullStack Overflow