JSON Parser error.

Question

Hi Everyone,

I am using the json parser from json.org to handle data from my application. The problem is that the parser cannot handle some json formats.

One request receives the data below.

  <?php

  $obj = array("cities"=>array("city1","city2","city3","city4","city5"));

  echo json_encode($obj);

  ?>

Results in the json below

{
"cities": ["city1","city2","city3","city4","city5"] 
}

the code below handles the above data

  var data = json_parse(XMLHttpRequestObject.responseText, function (key, value){

  alert(key +' = '+value);

  });

The parser fails and throws an error.

Does anyone know how to handle such an object.

Answer 1

I executed the following for a quick test and it seems to work:

var text = '{ "cities": ["city1","city2","city3","city4","city5"] }';
var data = json_parse(text, function (key, value){
  document.write(key + ' = ' + value + '<br/>');
});
document.write('result = ' + data);

It recursively walks the structure and the result is this:

0 = city1
1 = city2
2 = city3
3 = city4
4 = city5
cities = ,,,,
= [object Object]
result = undefined

What is in your XMLHttpRequestObject.responseText field?

Also, aren't you supposed to return a value from your function(key, value)?

Answer 2

I'd wager that the problem lies in your data. The '' before city3 is wrong.

It would help if you include some information on the error thrown.

Answer 3

You need to put your keys and values into double quotes:

{
"cities": ["city1","city2","city3","city4","city5"] 
}

A value can be a string in double quotes, or a number, or true or false or null, or an object or an array. These structures can be nested.

You can use jsonlint to validate the code.

Answer 4

The parser fails because the JSON data is malformed. There are two quotes in front of city3 and the starting quote for city4 is missing.

{
cities: ['city1','city2','city3','city4','city5'] 
}

Are you in control of the code that generates this output? It looks like it's being built by hand, while if possible it should be generated using a JSON library.

PHP example:

$output = array(
  'cities' => array('city1', 'city2', 'city3', 'city4', 'city5')
);
echo json_encode($output);

Output:

{"cities":["city1","city2","city3","city4","city5"]}

Answer 5

The problem seems to be in your application's json encoding algorithm.

Since you did't specify the application language, I cannot tell you the exact function/method to use, but I suggest you to use standard json encoding techniques instead reinventing the wheel.

For example in php you can use the json_encode standard function of one of the many encoding libraries in the open source world.