Javascript - JSON.parse: unexpected end of data - Error when using valid JSON. What am I doing wrong?

Question

So, I've found similar questions about JQuery in which you do not need to parse. Since I am using the AJAX XMLHttpRequest, from what I understand, the parse is necessary. The error is given on the line:

text = JSON.parse(jsonGet.responseText);

Error:

JSON.parse: unexpected end of data  
text = JSON.parse(jsonGet.responseText);

Relevant parts of the function:

function populateList(){
//retrieves list from the server, adds it to the option box
    if(toggle == 0){
        var jsonGet = new XMLHttpRequest();
        jsonGet.open("GET","./json/GetAllEvents.php",true);
        jsonGet.onreadystatechange = function () {
                text = JSON.parse(jsonGet.responseText);   //ERROR HERE
                //updating html with data received
        };
        jsonGet.send();
        toggle = 1;
    } else {}

};

The JSON returned looks like this (without the line breaks):

{"success":true,
"number_of_rows":2,
"data":[
    {"id":"7","event_name":null,"day":3,"start_time":510,"end_time":617},
    {"id":"8","event_name":null,"day":1,"start_time":510,"end_time":617}
]}

JSONLint says that the above is valid. I guess I will take a look into whether XMLHttpRequest does anything strange. Firefox continues to function (even though firebug shows the error), IE9 stops at this point though.

I'm pretty stumped. Any help is appreciated.

Answer 1

在解析响应之前，您必须检查jsonGet.readyState==4 && jsonGet.status==200 。