javascript - Recursive Function not working correctly -

i have recusive function supposed loop through json object , output expression. however, recusion seems off because it's outputting field1 != '' , field3 == '' when should outputting field1 != '' , field2 == '' , field3 == ''

i've tried couple different things , way can work creating global variable outstring instead of passing function. off? when step through it, see correct result once stack reverses, start resetting outstring , stack again leaves out middle (field2).

jsfiddle

function buildstring(json, outstring) {         var andor = json.condition;     (var rule in json.rules) {         if (json.rules[rule].hasownproperty("condition")) {             buildstring(json.rules[rule], outstring);         } else {             var field = json.rules[rule].id;             var operator = json.rules[rule].operator;             var value = json.rules[rule].value == null ? '' : json.rules[rule].value;             outstring += field + ' ' + operator + ' ' + value;             if (rule < json.rules.length - 1) {                 outstring += ' ' + andor + ' ';             }         }     }     return outstring; }  var jsonobj = {"condition":"and","rules":[{"id":"field1","operator":"!= ''","value":null},{"condition":"and","rules":[{"id":"field2","operator":"== ''","value":null}]},{"id":"field3","operator":"== ''","value":null}]};  $('#mydiv').text(buildstring(jsonobj, "")); 

the function has return of string.

when call function recursively within itself, aren't doing returned string instance, calling function has return to

change:

    if (json.rules[rule].hasownproperty("condition")) {        buildstring(json.rules[rule], outstring);     }  

to

    if (json.rules[rule].hasownproperty("condition")) {        // include returned value in concatenated string        outstring += buildstring(json.rules[rule], outstring);     } 

demo