How can I catch JSON parsing errors in JQuery?

Question

In the following code, if the JSON I am trying to read in has a slight syntax error somewhere, then it simply doesn't say anything, I can't find any error shown in Chrome or Firefox which is telling me that it cannot parse the JSON field. Even this try/catch doesn't work.

How can I get my code to do something specific if the JSON cannot be parsed?

function init() {
    elemFront = $('div.flashcard div.bodyFront');
    elemBack = $('div.flashcard div.bodyBack');
    console.log('before');
    try {
        console.log('inside try');
        $.getJSON('data.txt', function(jsonResult) {
            console.log(jsonResult);
        });
    } 
    catch(err) {
        console.log('error');
    }
    console.log('after');
}

Addendum

Thanks @sagi, that worked, here's the code that catches syntax issues with JSON data:

$.get('data.txt', {}, function(data, response){
    var jsonResult;
    try {
        jsonResult = JSON.parse(data);
    }
    catch (e) {
        $('div.header').html('<span style="color:red">cannot load data because: "'+e+'"</span>');
    };
    $('div.bodyFront').html(jsonResult['one']);
});

$.getJSON uses AJAX, which is asynchronous. The parsing happens in jQuery's internal callback function, which is outside the scope of the try block. — Barmar
– Barmar, Commented May 23, 2013 at 16:35

Sagish · Accepted Answer · 2013-05-23 16:40:26Z

14

if you are unsure of the response, you shouldn't use $.getJSON, instead you might want to do something like this

$.get('...', {}, function(data, response){
  var jsonResult;
  try {
    jsonResult = JSON.parse(data);
  }
  catch (e) {
    console.log("error: "+e);
  };
  // the rest of your code
});

answered May 23, 2013 at 16:40

Sagish

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2 Comments

geotheory Over a year ago

This still doesn't catch the error as there's apparently no timeout for the call.

César León Over a year ago

This fails if the response is a valid json JSON. SyntaxError: Unexpected token o in JSON at position 1

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