ryandlf ryandlf - 4 months ago 16
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]);
break;
case 'Email':
currentArray = currentArray.email;
mappedObj = mapEmail(jsonResponse[i]);
break;
case 'Address':
currentArray = currentArray.address;
mappedObj = mapAddress(jsonResponse[i]);
break;
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.

Answer

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.

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