ryandlf ryandlf - 2 months ago 11x
Javascript Question

Mapping JSON Objects to Javascript Objects

When using AJAX, I tend to pass objects from my server to Javascript in the form of JSON objects (aka Javascript). Certain functions within my Javascript rely on the specific type of object I am using. For instance, lets use a phone number for example. I have a constructor:

function PhoneNumber(number, type, isPrimary, contactId, id, className) {
this.number = number;
this.type = type;
this.isPrimary = isPrimary;
this.contactId = contactId;
this.id = id;
this.className = className;

Which I use when creating a phone number object in my Javascript. In some situations I don't create the object in JS, I get the object from the server so it comes in the form of a generic object with the exact same fields. So when my code relies on the specific type by using something such as this:

var objType = objArray[i].constructor.name;
var mappedObj;

switch(objType) {
case 'PhoneNumber':
currentArray = currentArray.phone;
//Convert response to javascript object.
mappedObj = mapPhone(jsonResponse[i]);
case 'Email':
currentArray = currentArray.email;
mappedObj = mapEmail(jsonResponse[i]);
case 'Address':
currentArray = currentArray.address;
mappedObj = mapAddress(jsonResponse[i]);
case 'Website':
currentArray = currentArray.website;
mappedObj = mapWebsite(jsonResponse[i]);

In this situation, I check the name of the objects constructor and set certain variables based on that name. If the object I check the name on is a JSON from the server, it simply gives me a generic "Object" response and thus the code does not work. I get around this by using a mapping function for each object such as:

function mapPhone(phoneObj) {
var id = phoneObj.id;
var contactId = phoneObj.contactId;
var number = phoneObj.number;
var type = phoneObj.type;
var primary = phoneObj.isPrimary;
var className = phoneObj.className;
var phoneNumber = new PhoneNumber(number, type, primary, contactId, id, className);
return phoneNumber;

This works just fine, but to me seems a little redundant. Is this the best way to solve the JSON Object problem, or is there a better solution? I understand this is more of a "Am I doing this the best way possible" type of question, but I repeat this type of logic CONSTANTLY in my Javascript code and I figure I might as well get another opinion or two on whether or not its the proper way to do this before I have to spend hour upon hour fixing it in the future.

EDIT: I ended up accepting a jQuery solution because I happen to use jQuery in my project. There are however multiple solutions that also worked for me before I found the jQuery option. They just weren't quite as clean and efficient.


The following requires you to have the same properties in your object and your JSON object.

var phoneNumber = $.extend(new PhoneNumber(), yourJSONObject);

This basically creates a new PhoneNumber object and then copies all properties from your JSON object onto it. The $.extend() method is from jQuery, but you could also use as similar method from e.g. Underscore.js or one of the other js libraries/frameworks.