JSON.stringify() with collection in backbone.js - backbone.js

Question

Can someone explain how JSON.stringify() magically ONLY stringifies JSON as fetched by URL and does NOT bother with other backbone-specific parts of the full collection object?
I am curious about underlying implementation and/or design patterns that explain this very impressive capability. I had to use json2.js to get stringify functionality, so I don't think backbone is overriding or decorating stringify.
I discovered that if I pass a collection directly to JS OBJECT code, the code "sees" model keys and other backbone-specific parts of a collection object, whereas if I perform JSON.stringify THEN jquery.parseJSON on that stringified object, my code "sees" only the JSON as returned by URL.
Code:
enter code here
$(function () {
var Person = Backbone.Model.extend({
initialize: function () {
// alert("Model Init");
}
}),
PersonList = Backbone.Collection.extend({
model: Person,
url: '/Tfount_Email/Email/SOAInbox',
initialize: function () {
// alert("Collections Init");
}
}),
personlist = new PersonList();
personlist.fetch({
error: function () {
alert("Error fetching data");
},
success: function () {
// alert("no error");
}
}).complete(function () {
// first call to makeTable w collection obj, we see MORE than just the JSON returned by URL
makeTable(personlist);
// stringify then parse, we see only JSON returned by URL
jsonString = JSON.stringify(personlist);
var plistJSON = jQuery.parseJSON(jsonString);
makeTable(plistJSON);
});
});
function makeTable(obj) {
var type = typeof obj
if (type == "object") {
for (var key in obj) {
alert("key: " + key)
makeTable(obj[key])
}
} else {
alert(obj)
}
}

Answer 1

This is the intended and by-design behavior of JSON.Stringify. From Douglas Crockford's JSON2.js file:
When an object value is found, if the object contains a toJSON method, its toJSON method will be called and the result will be stringified.
https://github.com/douglascrockford/JSON-js/blob/master/json2.js#L38-39
When you call JSON.stringify on a Backbone.Collection, it calls that collection's toJSON method, as described by this comment.