Question

I have a php-site with a form on which i output preselected values via php. On form submit I want to check which values have changed and just submit these via javascript.

These are the preselected values I passed over from php. It’s important that I keep the associative array structure.

var pbData = jQuery.parseJSON("{
"GameMode":"DEATHMATCH",
"Current Map":"VEGAS JUNKYARD",
"Current Missions":["VEGAS JUNKYARD","VILLA","PRESIDIO","KILL HOUSE","MURDERTOWN","CQB TRAINING","STREETS","THREE KINGDOMS CASINO","IMPORT\/EXPORT;"],
"RoundDuration":"3 minutes"}");

I marked the error in the code.

<script>
function displayVars(){
var form = document.getElementById('settings');
var elems = form.elements;
var txt = "";
for (var index = 0; index < elems.length; index++){
    var selIndex = elems[index].selectedIndex;
    if (typeof selIndex !== "undefined"){
        //the Index Name in the json-object and the name of the form-field are the same 
        var idxName = elems[index].name;
//HERE is the problem. I want to access the subobject via a variablename, so i can iterate through it, but that doesnt work.
        console.log ("pbData default = "+pbData.idxName); //always undefined
        if (elems[index].value !== pbData.idx_name){
            //building a POST-Url
            txt = txt + elems[index].name + "=" + elems[index].options[selIndex].value+"&";
        }
    }
}
console.log (txt);
return false;
}
</script>

I know that I could do this differently, also with jQuery. In my case as I have the preselected values as a php-variable in any case, i think it’s easier like this.
I would really like to know how I can iterate through the subobjects via a variable that contains the object names.

Answer 1

This is due to how you’e trying to access the property of the (JSON) object. Consider

var o1 = {idxName: true},
    o2 = {foo : 'bar'},
    idxName = 'foo';

o1.idxName;  // true
o2.idxName;  // undefined
o2[idxName]; // 'bar'

You need to access the property via pbData[idxName].

---

Additionally, you’re not escaping quotes in your JSON string, and line breaks need to be escaped as follows

var pbData = jQuery.parseJSON("{\
\"GameMode\":\"DEATHMATCH\",\
\"Current Map\":\"VEGAS JUNKYARD\",\
\"Current Missions\":[\"VEGAS JUNKYARD\",\"VILLA\",\"PRESIDIO\",\"KILL HOUSE\",\"MURDERTOWN\",\"CQB TRAINING\",\"STREETS\",\"THREE KINGDOMS CASINO\",\"IMPORT\/EXPORT;\"],\
\"RoundDuration\":\"3 minutes\"}");