CODEWITHSUNDEEP
javascriptjqueryinternet-explorer
Scarface
Scarface

Reputation: 3923

'length' is null or not an object? IE 8

I get the following error in IE8:

length is null or not an object

Anyone have any ideas? Feedback greatly appreciated.

function refresh() {
  $.getJSON(files+"handler.php?action=view&load=update&time="+lastTimeInterval+"&username="+username+"&topic_id="+topic_id+"&t=" + (new Date()), function(json) {
    if(json.length) {
      for(i=0; i < json.length; i++) {
        $('#list').prepend(prepare(json[i]));
        $('#list-' + count).fadeIn(1500);
      }
      var j = i-1;
      lastTimeInterval = json[j].timestamp;
    }
  });
}

Upvotes: 8

Views: 20385

Answers (6)

Pointy
Pointy

Reputation: 413846

Just check for the object being null or empty:

if (json && json.length) {
  // ...
}

C'mon gang this was glaringly obvious :-)

Upvotes: 12

meder omuraliev
meder omuraliev

Reputation: 186662

A JSON is an object, you seem to be treating it like an array. Does it really have a length property? Show us the JSON?

You might need to use a for..in instead.

EDIT: Can you make the JSON from the backend structure like so?

({
    "foo": [] 
})

Upvotes: 0

Mark Schultheiss
Mark Schultheiss

Reputation: 34197

pop the JSON in a span then clip it and paste it here so we can see it:

<span id="JSObject2">empty</span>

with the json2.js from here: (link for it at bottom of the page) http://www.json.org/js.html

myJSON = JSON.stringify(json);
$('#JSObject2').text(myJSON);

Using that, we can help you better, and you can see what you have!

Upvotes: 1

rfunduk
rfunduk

Reputation: 30442

JSON objects (returned by jQuery or otherwise) do not have a length property. You'll need to iterate over the properties, most likely, or know the structure and simply pull out what you want:

$.getJSON( ..., ..., function( json ) {
  for( var prop in json ) {
    if( !json.hasOwnProperty( prop ) ) { return; }
    alert( prop + " : " + json[prop] );
  }
} );

Alternatively, grab a library like json2 and you'll be able to stringify the object for output/debugging.

Upvotes: 1

George
George

Reputation: 581

First thing that comes to mind is that length is not a property of whatever json is. What is the json variable supposed to be anyway?

Upvotes: 0

Matt Huggins
Matt Huggins

Reputation: 83289

What does your returned JSON look like? If you're returning an object, length might not be explicitly defined, whereas if you're returning an array, it should be defined automatically.

Upvotes: 0

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