Question

I use ajax to run MySQL query and echo json_encode result, so that I can get a JSON object:

$.ajax({
    url: phpUrl,
    data: command,
    dataType: 'json',
    async: true,
    success: function(jsonData) {
        //XXX
    }

The JSON object should be like: {cols: [XXXX], rows: [XXXX]}.

Sometimes there is error msg from MySQL query, so the returned JSON object is not valid. How can I determine if the returned JSON object is valid or not?

edit

In http://api.jquery.com/jQuery.ajax/, it says “the JSON data is parsed in a strict manner; any malformed JSON is rejected and a parse error is thrown”. How to handle the parse error?

Answer 1

Something like this should work:

$.ajax({
    url: phpUrl,
    data: command,
    dataType: 'json',
    async: true,
    success: function(jsonData) {
        //XXX
    },
    error:function(xhr,err){
        if (err=='parsererror') alert('invalid json');
    }
);