var tc_event;

function changeValue(TC_Event) {

var tcInfo = JSON.parse(TC_Info);
var userId = tcInfo.userId;
var ipAddress = tcInfo.ipAddress;
var mydata = JSON.parse(TC_Event);
var teststring = "lowercase";

for (var index in mydata) {
var field = mydata[index];

if (field.name === 'UserID') {
field.value = userId;
} else if (field['name'] == 'UserIP') {
field.value = ipAddress;
} 
}

tc_event = JSON.stringify(mydata);

return tc_event;
}
changeValue(TC_Event);