Object is created but seems to be sharing a reference

Object is created but seems to be sharing a reference - javascript

I am building an editor, in the editor when you press play it converts a bunch of objects to a Prefab (which explains to my engine how to build an object). When I then stop them I would like to rebuild the Prefab again and it should be back to its original state (before play was pressed). The issue that I am having is that when stop is pressed the items don't go back to their original state. They seem to stay in the state that they are in when stop was pressed.
Here is the class that I am using to convert Prefabs back and forth:
class Prefab {
public name: string;
public components: PrefabComponent[] = [];
public static create(gameObject: GameObject): Prefab {
let prefab = new Prefab;
prefab.name = gameObject.name;
gameObject.components.forEach(comp => {
let prefabComp = new PrefabComponent;
prefabComp.name = comp.name;
for (let c in comp) {
let prefabProp = new PrefabProperty;
prefabProp.name = c;
if (typeof comp[c] == 'object') {
prefabProp.value = Object.create(comp[c]);
} else {
prefabProp.value = comp[c];
}
prefabComp.properties.push(prefabProp);
}
prefab.components.push(prefabComp);
});
return prefab;
}
public static toObject(prefab: Prefab): GameObject {
let gameObject = new GameObject(prefab.name);
prefab.components.forEach(comp => {
let newComp;
if (comp.name.toLowerCase() != 'transform') {
newComp = gameObject.addComponent(comp.name);
}
if (!newComp) {
newComp = gameObject.getComponent(comp.name);
}
comp.properties.forEach(prop => {
if (prop.value instanceof Sprite) {
newComp[prop.name] = Sprite.create(prop.value.path);
} else if (typeof prop.value == 'object') {
newComp[prop.name] = Object.create(prop.value);
} else {
newComp[prop.name] = prop.value;
}
});
});
return gameObject;
}
}
class PrefabComponent {
public name: string;
public properties: PrefabProperty[] = [];
}
class PrefabProperty {
public name: string;
public value: any;
}
Here is how I am starting and stopping the game:
play.addEventListener('click', (event) => {
event.preventDefault();
// Game has started
// Stop was pressed
if (game instanceof SpyNginMain) {
game.stopGame();
game = null;
play.classList.remove('active');
pause.classList.remove('active');
// Reset the editor
EditorObjectManager.clear();
prefabs.forEach(prefab => {
EditorObjectManager.addItem(Prefab.toObject(prefab));
});
updateScene();
}
// Game has not started
// Play was pressed
else {
game = new SpyNginMain();
prefabs = [];
EditorObjectManager.items.forEach(item => {
prefabs.push(Prefab.create(item));
});
game.init(scene, prefabs);
game.startGame();
play.classList.add('active');
}
});
The issue seems to be when I try to convert Object with the PrefabProperty class. I think that it isn't creating an instance but is creating a reference to the original, but I am not sure...

Your create method will certainly retain references to the original object because of the following code:
if (typeof comp[c] == 'object') {
prefabProp.value = Object.create(comp[c]);
} else {
prefabProp.value = comp[c];
}
The Object.create call creates a new object with the original object as its prototype, so if you subsequently add/modify/delete a property in the original object, the changes will also appear in the newly created object.
I think what you meant to do here is to clone the original object? There are many existing implementations for cloning (eg lodash's cloneDeep).
I would replace all five lines quoted above with a single clone(comp[c]) call, since your typeof check is not reliable in other ways too (eg typeof null == 'object' is true, typeof [1,2,3] == 'object' is true, etc).

This might just be a typescript thing but seeing this without parenthesis looks incorrect:
let prefabComp = new PrefabComponent;
I believe it should be:
let prefabComp = new PrefabComponent();
Also this line here: newComp[prop.name] = prop.value; if prop.value is an object, that component would get referenced from the old one.
A good way to see if the object is the same one is ===.
const a = {'a': 'hello'};
console.log(a === a); // true
const b = {'a': 'hello'};
console.log(a === b); // false

Related

How to use Proxy to intercept every function of an object in JavaScript or E6?

I have a class A, defined like below.(All sample code is simplified for privacy)
class A{
Func1(){
}
Func2(){
}
Func3(){
}
}
And I want to make every function in A running after another function Func4();
So I write a fuction to intercept through Proxy like below:
_Intercept(object) {
if (object === undefined || object === null) {
throw new Error('intercept need non null object');
}
const objectPrototypes = Object.getPrototypeOf(object);
const objectPropertyNames = Object.getOwnPropertyNames(objectPrototypes);
for (const index in objectPropertyNames) {
const protoName = objectPropertyNames[index];
if (!object.__proto__.hasOwnProperty(protoName)) {
continue;
}
let originalFunction = object.__proto__[protoName];
if (originalFunction === undefined || originalFunction === null) {
continue;
}
if (typeof (originalFunction) !== 'function') {
continue;
}
if (protoName === 'constructor') {
continue;
}
console.log(object.__proto__[protoName]);
object.__proto__[protoName] = new Proxy(originalFunction, {
apply(target, thisArg, argArray) {
console.log("you intercept this func");
return Reflect.apply(...arguments);
}
});
}
return object;
And in another main.js, I write code like this:
var a=new A();
a = _Intercept(a);
var b=new B();
b = _Intercept(b);
a.Func1();
But in chrome console, there output two lines "you intercept this func"
How could this happen? I've only apply a.Func1() clearly, why print two lines??
And when I try delete "b = _Intercept(b)" in main.js or delete " return Reflect.apply(...arguments);" in function _Intercept, it will only print one line.
Is anyone know about this situation ? Is my wrong use?Or ES6 Proxy bug?
Or Someone gimme some better dynamic proxy in javascript rather than Proxy in ES6??
I've tried another version before, use objectPrototypes rather than proto, but it works no good.
objectPrototypes[name] = new Proxy(originalFunction, handler);

does javascript have something equivalent to Python's `id` function? [duplicate]

I need to do some experiment and I need to know some kind of unique identifier for objects in javascript, so I can see if they are the same. I don't want to use equality operators, I need something like the id() function in python.
Does something like this exist ?

Update My original answer below was written 6 years ago in a style befitting the times and my understanding. In response to some conversation in the comments, a more modern approach to this is as follows:
(function() {
if ( typeof Object.id != "undefined" ) return;
var id = 0;
Object.id = function(o) {
if ( typeof o.__uniqueid != "undefined" ) {
return o.__uniqueid;
}
Object.defineProperty(o, "__uniqueid", {
value: ++id,
enumerable: false,
// This could go either way, depending on your
// interpretation of what an "id" is
writable: false
});
return o.__uniqueid;
};
})();
var obj = { a: 1, b: 1 };
console.log(Object.id(obj));
console.log(Object.id([]));
console.log(Object.id({}));
console.log(Object.id(/./));
console.log(Object.id(function() {}));
for (var k in obj) {
if (obj.hasOwnProperty(k)) {
console.log(k);
}
}
// Logged keys are `a` and `b`
If you have archaic browser requirements, check here for browser compatibility for Object.defineProperty.
The original answer is kept below (instead of just in the change history) because I think the comparison is valuable.
You can give the following a spin. This also gives you the option to explicitly set an object's ID in its constructor or elsewhere.
(function() {
if ( typeof Object.prototype.uniqueId == "undefined" ) {
var id = 0;
Object.prototype.uniqueId = function() {
if ( typeof this.__uniqueid == "undefined" ) {
this.__uniqueid = ++id;
}
return this.__uniqueid;
};
}
})();
var obj1 = {};
var obj2 = new Object();
console.log(obj1.uniqueId());
console.log(obj2.uniqueId());
console.log([].uniqueId());
console.log({}.uniqueId());
console.log(/./.uniqueId());
console.log((function() {}).uniqueId());
Take care to make sure that whatever member you use to internally store the unique ID doesn't collide with another automatically created member name.

So far as my observation goes, any answer posted here can have unexpected side effects.
In ES2015-compatible enviroment, you can avoid any side effects by using WeakMap.
const id = (() => {
let currentId = 0;
const map = new WeakMap();
return (object) => {
if (!map.has(object)) {
map.set(object, ++currentId);
}
return map.get(object);
};
})();
id({}); //=> 1

Latest browsers provide a cleaner method for extending Object.prototype. This code will make the property hidden from property enumeration (for p in o)
For the browsers that implement defineProperty, you can implement uniqueId property like this:
(function() {
var id_counter = 1;
Object.defineProperty(Object.prototype, "__uniqueId", {
writable: true
});
Object.defineProperty(Object.prototype, "uniqueId", {
get: function() {
if (this.__uniqueId == undefined)
this.__uniqueId = id_counter++;
return this.__uniqueId;
}
});
}());
For details, see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/defineProperty

Actually, you don't need to modify the object prototype and add a function there. The following should work well for your purpose.
var __next_objid=1;
function objectId(obj) {
if (obj==null) return null;
if (obj.__obj_id==null) obj.__obj_id=__next_objid++;
return obj.__obj_id;
}

For browsers implementing the Object.defineProperty() method, the code below generates and returns a function that you can bind to any object you own.
This approach has the advantage of not extending Object.prototype.
The code works by checking if the given object has a __objectID__ property, and by defining it as a hidden (non-enumerable) read-only property if not.
So it is safe against any attempt to change or redefine the read-only obj.__objectID__ property after it has been defined, and consistently throws a nice error instead of silently fail.
Finally, in the quite extreme case where some other code would already have defined __objectID__ on a given object, this value would simply be returned.
var getObjectID = (function () {
var id = 0; // Private ID counter
return function (obj) {
if(obj.hasOwnProperty("__objectID__")) {
return obj.__objectID__;
} else {
++id;
Object.defineProperty(obj, "__objectID__", {
/*
* Explicitly sets these two attribute values to false,
* although they are false by default.
*/
"configurable" : false,
"enumerable" : false,
/*
* This closure guarantees that different objects
* will not share the same id variable.
*/
"get" : (function (__objectID__) {
return function () { return __objectID__; };
})(id),
"set" : function () {
throw new Error("Sorry, but 'obj.__objectID__' is read-only!");
}
});
return obj.__objectID__;
}
};
})();

Typescript version of #justin answer, ES6 compatible, using Symbols to prevent any key collision and added into the global Object.id for convenience. Just copy paste the code below, or put it into an ObjecId.ts file you will import.
(enableObjectID)();
declare global {
interface ObjectConstructor {
id: (object: any) => number;
}
}
const uniqueId: symbol = Symbol('The unique id of an object');
export function enableObjectID(): void {
if (typeof Object['id'] !== 'undefined') {
return;
}
let id: number = 0;
Object['id'] = (object: any) => {
const hasUniqueId: boolean = !!object[uniqueId];
if (!hasUniqueId) {
object[uniqueId] = ++id;
}
return object[uniqueId];
};
}
Example of usage:
console.log(Object.id(myObject));

jQuery code uses it's own data() method as such id.
var id = $.data(object);
At the backstage method data creates a very special field in object called "jQuery" + now() put there next id of a stream of unique ids like
id = elem[ expando ] = ++uuid;
I'd suggest you use the same method as John Resig obviously knows all there is about JavaScript and his method is based on all that knowledge.

For the purpose of comparing two objects, the simplest way to do this would be to add a unique property to one of the objects at the time you need to compare the objects, check if the property exists in the other and then remove it again. This saves overriding prototypes.
function isSameObject(objectA, objectB) {
unique_ref = "unique_id_" + performance.now();
objectA[unique_ref] = true;
isSame = objectB.hasOwnProperty(unique_ref);
delete objectA[unique_ref];
return isSame;
}
object1 = {something:true};
object2 = {something:true};
object3 = object1;
console.log(isSameObject(object1, object2)); //false
console.log(isSameObject(object1, object3)); //true

I faced the same problem and here's the solution I implemented with ES6
code
let id = 0; // This is a kind of global variable accessible for every instance
class Animal {
constructor(name){
this.name = name;
this.id = id++;
}
foo(){}
// Executes some cool stuff
}
cat = new Animal("Catty");
console.log(cat.id) // 1

I've used code like this, which will cause Objects to stringify with unique strings:
Object.prototype.__defineGetter__('__id__', function () {
var gid = 0;
return function(){
var id = gid++;
this.__proto__ = {
__proto__: this.__proto__,
get __id__(){ return id }
};
return id;
}
}.call() );
Object.prototype.toString = function () {
return '[Object ' + this.__id__ + ']';
};
the __proto__ bits are to keep the __id__ getter from showing up in the object. this has been only tested in firefox.

Notwithstanding the advice not to modify Object.prototype, this can still be really useful for testing, within a limited scope. The author of the accepted answer changed it, but is still setting Object.id, which doesn't make sense to me. Here's a snippet that does the job:
// Generates a unique, read-only id for an object.
// The _uid is generated for the object the first time it's accessed.
(function() {
var id = 0;
Object.defineProperty(Object.prototype, '_uid', {
// The prototype getter sets up a property on the instance. Because
// the new instance-prop masks this one, we know this will only ever
// be called at most once for any given object.
get: function () {
Object.defineProperty(this, '_uid', {
value: id++,
writable: false,
enumerable: false,
});
return this._uid;
},
enumerable: false,
});
})();
function assert(p) { if (!p) throw Error('Not!'); }
var obj = {};
assert(obj._uid == 0);
assert({}._uid == 1);
assert([]._uid == 2);
assert(obj._uid == 0); // still

This one will calculate a HashCode for each object, optimized for string, number and virtually anything that has a getHashCode function. For the rest it assigns a new reference number.
(function() {
var __gRefID = 0;
window.getHashCode = function(ref)
{
if (ref == null) { throw Error("Unable to calculate HashCode on a null reference"); }
// already cached reference id
if (ref.hasOwnProperty("__refID")) { return ref["__refID"]; }
// numbers are already hashcodes
if (typeof ref === "number") { return ref; }
// strings are immutable, so we need to calculate this every time
if (typeof ref === "string")
{
var hash = 0, i, chr;
for (i = 0; i < ref.length; i++) {
chr = ref.charCodeAt(i);
hash = ((hash << 5) - hash) + chr;
hash |= 0;
}
return hash;
}
// virtual call
if (typeof ref.getHashCode === "function") { return ref.getHashCode(); }
// generate and return a new reference id
return (ref["__refID"] = "ref" + __gRefID++);
}
})();

If you came here because you deal with class instances like me you can use static vars/methods to reference instances by a custom unique id:
class Person {
constructor( name ) {
this.name = name;
this.id = Person.ix++;
Person.stack[ this.id ] = this;
}
}
Person.ix = 0;
Person.stack = {};
Person.byId = id => Person.stack[ id ];
let store = {};
store[ new Person( "joe" ).id ] = true;
store[ new Person( "tim" ).id ] = true;
for( let id in store ) {
console.log( Person.byId( id ).name );
}

Here's a variant of Justin Johnson's answer that provides a scalability benefit when you are creating billions of objects for which you want the ID.
Specifically, rather than solely using a 1-up counter (that might overflow the representational limits of Number, and can't be cycled without risking reusing an ID), we register the object and its newly generated ID with a FinalizationRegistry, such that, at some point after the object is garbage collected, the ID is returned to a freelist for reuse by a newly created object (Python's id function can also return the same ID for multiple objects, so long as the existence of the two objects does not overlap in time).
Limitations:
It only works on objects, not JS primitives (this is somewhat reasonable; unlike Python, where everything is an object, JS primitives typically aren't, and the id function logically only works on objects, since primitives need not "exist" in any reasonably identifiable way).
If the code creates (without discarding) billions of objects, asks for their IDs, then releases them all at once and never asks for an ID again, the recovered IDs in the freelist constitute a memory leak of sorts. Hopefully the JS optimizer stores them efficiently, so the cost remains a small fraction of what the objects themselves cost, but it's still a cost. In cases where objects with IDs are regularly created and destroyed, the wasted memory is roughly tied to the maximum number of such ID-ed objects in existence at any given point in time.
If those limitations aren't a problem though, this works fairly well. I modified the testing code a bit to hand control back to the event loop (and hopefully the garbage collector) now and again while creating 10M garbage objects to ID, and on my browser, nearly half the object IDs get reclaimed for reuse; the final loop making five objects and IDing them produces IDs just above 1M, when over 2M objects had IDs generated at some point. In a realistic scenario with meaningful code executing and real async usage I'd expect better results simply because there would be more opportunities for the finalization registry to perform cleanup.
async function sleep(ms) {
await _sleep(ms);
}
function _sleep(ms) {
return new Promise((resolve) => setTimeout(resolve, ms));
}
(function() {
if ( typeof Object.id != "undefined" ) return;
var freelist = []; // Stores previously used IDs for reuse when an object with
// an ID is garbage collected, so creating and dropping billions
// of objects doesn't consume all available IDs
const registry = new FinalizationRegistry((freeid) => {
freelist.push(freeid);
});
var id = 0;
Object.id = function(o) {
if ( typeof o.__uniqueid != "undefined" ) {
return o.__uniqueid;
}
Object.defineProperty(o, "__uniqueid", {
value: freelist.length ? freelist.pop() : ++id,
enumerable: false,
// This could go either way, depending on your
// interpretation of what an "id" is
writable: false
});
registry.register(o, o.__uniqueid); // Sometime after o is collected, its ID
// will be reclaimed for use by a new object
return o.__uniqueid;
};
})();
var obj = { a: 1, b: 1 };
console.log(Object.id(obj));
console.log(Object.id([]));
console.log(Object.id({}));
console.log(Object.id(/./));
var idsum = 0; // So we do something real to prevent optimizing out code
// Make a ton of temporary objects with IDs, handing control back to the event loop
// every once in a while to (hopefully) see some IDs returned to the pool
for (var i = 0; i < 1000000; ++i) {
idsum += Object.id({c: i});
}
sleep(10).then(() => {
console.log(Object.id(function() { console.log("Hey"); }));
for (var i = 1000000; i < 2000000; ++i) {
idsum += Object.id({c: i});
}
console.log(Object.id(function() { console.log("There"); }));
sleep(10).then(() => {
for (var i = 0; i < 5; ++i) {
console.log(Object.id([i]));
}
console.log(idsum);
});
});
for (var k in obj) {
if (obj.hasOwnProperty(k)) {
console.log(k);
}
}
// Logged keys are `a` and `b`

Javascript scoping for object

I get that everything in Javascript is an object, but how is possible to declare one variable in one scope; I mean merely as a variable and suddenly start using it as an object assigning some properties "INSIDE" other functions. How does scoping for this case work?
https://github.com/ariya/esprima/blob/master/esprima.js
In this code, the extra variable is only declared without being given any properties:
var Token,
extra;
And suddenly it starts being used by object as follows:
function addComment(type, value, start, end, loc) {
var comment, attacher;
assert(typeof start === 'number', 'Comment must have valid position');
// Because the way the actual token is scanned, often the comments
// (if any) are skipped twice during the lexical analysis.
// Thus, we need to skip adding a comment if the comment array already
// handled it.
if (state.lastCommentStart >= start) {
return;
}
state.lastCommentStart = start;
comment = {
type: type,
value: value
};
if (extra.range) {
comment.range = [start, end];
}
if (extra.loc) {
comment.loc = loc;
}
extra.comments.push(comment);
if (extra.attachComment) {
attacher = {
comment: comment,
leading: null,
trailing: null,
range: [start, end]
};
extra.pendingComments.push(attacher);
}
}
The closest example that I can get for this extra to be initiated as object is from the following function:
function tokenize(code, options) {
var toString,
token,
tokens;
toString = String;
if (typeof code !== 'string' && !(code instanceof String)) {
code = toString(code);
}
delegate = SyntaxTreeDelegate;
source = code;
index = 0;
lineNumber = (source.length > 0) ? 1 : 0;
lineStart = 0;
length = source.length;
lookahead = null;
state = {
allowIn: true,
labelSet: {},
inFunctionBody: false,
inIteration: false,
inSwitch: false,
lastCommentStart: -1
};
extra = {};
// Options matching.
options = options || {};
// Of course we collect tokens here.
options.tokens = true;
extra.tokens = [];
extra.tokenize = true;
// The following two fields are necessary to compute the Regex tokens.
extra.openParenToken = -1;
extra.openCurlyToken = -1;
extra.range = (typeof options.range === 'boolean') && options.range;
extra.loc = (typeof options.loc === 'boolean') && options.loc;
if (typeof options.comment === 'boolean' && options.comment) {
extra.comments = [];
}
if (typeof options.tolerant === 'boolean' && options.tolerant) {
extra.errors = [];
}
if (length > 0) {
if (typeof source[0] === 'undefined') {
// Try first to convert to a string. This is good as fast path
// for old IE which understands string indexing for string
// literals only and not for string object.
if (code instanceof String) {
source = code.valueOf();
}
}
}
try {
peek();
if (lookahead.type === Token.EOF) {
return extra.tokens;
}
token = lex();
while (lookahead.type !== Token.EOF) {
try {
token = lex();
} catch (lexError) {
token = lookahead;
if (extra.errors) {
extra.errors.push(lexError);
// We have to break on the first error
// to avoid infinite loops.
break;
} else {
throw lexError;
}
}
}
filterTokenLocation();
tokens = extra.tokens;
if (typeof extra.comments !== 'undefined') {
tokens.comments = extra.comments;
}
if (typeof extra.errors !== 'undefined') {
tokens.errors = extra.errors;
}
} catch (e) {
throw e;
} finally {
extra = {};
}
return tokens;
}
But still it is only inside this function, not in the same scope as
var Token,
extra;
How is it possible just to declare a variable and only instantiate the properties inside a function? How is it shared between different scopes? Once given the properties in one function, is it shared to other scopes such as another scope in another function? So confusing.

Line #3658 sets it to an empty object:
extra = {};

Scoping has to do with the matching of identifiers (i.e. names) to the what they refer to. For an object created in one scope to be accessed from another, you merely need to have a name in each refer to the same thing (for example, by returning an object created in a function to its caller and having the caller assign it to a variable whose name is in its scope).

Ember model to json

I am looking for an efficient way to translate my Ember object to a json string, to use it in a websocket message below
/*
* Model
*/
App.node = Ember.Object.extend({
name: 'theName',
type: 'theType',
value: 'theValue',
})
The websocket method:
App.io.emit('node', {node: hash});
hash should be the json representation of the node. {name: thename, type: theType, ..}
There must be a fast onliner to do this.. I dont want to do it manualy since i have many attributes and they are likely to change..

As stated you can take inspiration from the ember-runtime/lib/core.js#inspect function to get the keys of an object, see http://jsfiddle.net/pangratz666/UUusD/
App.Jsonable = Ember.Mixin.create({
getJson: function() {
var v, ret = [];
for (var key in this) {
if (this.hasOwnProperty(key)) {
v = this[key];
if (v === 'toString') {
continue;
} // ignore useless items
if (Ember.typeOf(v) === 'function') {
continue;
}
ret.push(key);
}
}
return this.getProperties.apply(this, ret);
}
});
Note, since commit 1124005 - which is available in ember-latest.js and in the next release - you can pass the ret array directly to getProperties, so the return statement of the getJson function looks like this:
return this.getProperties(ret);

You can get a plain JS object (or hash) from an Ember.Object instance by calling getProperties() with a list of keys.
If you want it as a string, you can use JSON.stringify().
For example:
var obj = Ember.Object.create({firstName: 'Erik', lastName: 'Bryn', login: 'ebryn'}),
hash = obj.getProperties('firstName', 'lastName'), // => {firstName: 'Erik', lastName: 'Bryn'}
stringHash = JSON.stringify(hash); // => '{"firstName": "Erik", "lastName": "Bryn"}'

I have also been struggling with this. As Mirko says, if you pass the ember object to JSON.stringify you will get circular reference error. However if you store the object inside one property and use stringify on that object, it works, even nested subproperties.
var node = Ember.Object.create({
data: {
name: 'theName',
type: 'theType',
value: 'theValue'
}
});
console.log(JSON.stringify(node.get('data')));
However, this only works in Chrome, Safari and Firefox. In IE8 I get a stack overflow so this isn't a viable solution.
I have resorted to creating JSON schemas over my object models and written a recursive function to iterate over the objects using the properties in the schemas and then construct pure Javascript objects which I can then stringify and send to my server. I also use the schemas for validation so this solution works pretty well for me but if you have very large and dynamic data models this isn't possible. I'm also interested in simpler ways to accomplish this.

I modifed #pangratz solution slightly to make it handle nested hierarchies of Jsonables:
App.Jsonable = Ember.Mixin.create({
getJson: function() {
var v, json = {};
for (var key in this) {
if (this.hasOwnProperty(key)) {
v = this[key];
if (v === 'toString') {
continue;
}
if (Ember.typeOf(v) === 'function') {
continue;
}
if (App.Jsonable.detect(v))
v = v.getJson();
json[key] = v;
}
}
return json;
}
});

App.io.emit('node', {node: node.toJSON()});
Or if you have an ID property and want to include it:
App.io.emit('node', {node: node.toJSON({includeId: true})});

Will this work for you?
var json = JSON.stringify( Ember.getMeta( App.node, 'values') );
The false is optional, but would be more performant if you do not intend to modify any of the properties, which is the case according to your question. This works for me, but I am wary that Ember.meta is a private method and may work differently or not even be available in future releases. (Although, it isn't immediately clear to me if Ember.getMeta() is private). You can view it in its latest source form here:
https://github.com/emberjs/ember.js/blob/master/packages/ember-metal/lib/utils.js
The values property contains only 'normal' properties. You can collect any cached, computed properties from Ember.meta( App.node, false ).cached. So, provided you use jQuery with your build, you can easily merge these two objects like so:
$.extend( {}, Ember.getMeta(App.node, 'values'), Ember.getMeta(App.node, 'cache') );
Sadly, I haven't found a way to get sub-structures like array properties in this manner.

I've written an extensive article on how you can convert ember models into native objects or JSON which may help you or others :)
http://pixelchild.com.au/post/44614363941/how-to-convert-ember-objects-to-json
http://byronsalau.com/blog/convert-ember-objects-to-json/

I modified #Kevin-pauli solution to make it works with arrays as well:
App.Jsonable = Ember.Mixin.create({
getJson: function() {
var v, json = {}, inspectArray = function (aSome) {
if (Ember.typeof(aSome) === 'array') {
return aSome.map(inspectArray);
}
if (Jsonable.detect(aSome)) {
return aSome.getJson();
}
return aSome;
};
for (var key in this) {
if (this.hasOwnProperty(key)) {
v = this[key];
if (v === 'toString') {
continue;
}
if (Ember.typeOf(v) === 'function') {
continue;
}
if (Ember.typeOf(v) === 'array') {
v = v.map(inspectArray);
}
if (App.Jsonable.detect(v))
v = v.getJson();
json[key] = v;
}
}
return json;
}
});
I also made some further modification to get the best of both worlds. With the following version I check if the Jsonable object has a specific property that informs me on which of its properties should be serialized:
App.Jsonable = Ember.Mixin.create({
getJson: function() {
var v, json = {}, base, inspectArray = function (aSome) {
if (Ember.typeof(aSome) === 'array') {
return aSome.map(inspectArray);
}
if (Jsonable.detect(aSome)) {
return aSome.getJson();
}
return aSome;
};
if (!Ember.isNone(this.get('jsonProperties'))) {
// the object has a selective list of properties to inspect
base = this.getProperties(this.get('jsonProperties'));
} else {
// no list given: let's use all the properties
base = this;
}
for (var key in base) {
if (base.hasOwnProperty(key)) {
v = base[key];
if (v === 'toString') {
continue;
}
if (Ember.typeOf(v) === 'function') {
continue;
}
if (Ember.typeOf(v) === 'array') {
v = v.map(inspectArray);
}
if (App.Jsonable.detect(v))
v = v.getJson();
json[key] = v;
}
}
return json;
}
});
I am using this little tweak and I am happy with it. I hope it'll help others as well!
Thanks to #pangratz and #Kevin-Pauli for their solution!

Here I take #leo, #pangratz and #kevin-pauli solution a little step further. Now it iterates not only with arrays but also through has many relationships, it doesn't check if a value has the type Array but it calls the isArray function defined in Ember's API.
Coffeescript
App.Jsonable = Em.Mixin.create
getJson: ->
jsonValue = (attr) ->
return attr.map(jsonValue) if Em.isArray(attr)
return attr.getJson() if App.Jsonable.detect(attr)
attr
base =
if Em.isNone(#get('jsonProperties'))
# no list given: let's use all the properties
this
else
# the object has a selective list of properties to inspect
#getProperties(#get('jsonProperties'))
hash = {}
for own key, value of base
continue if value is 'toString' or Em.typeOf(value) is 'function'
json[key] = jsonValue(value)
json
Javascript
var hasProp = {}.hasOwnProperty;
App.Jsonable = Em.Mixin.create({
getJson: function() {
var base, hash, hashValue, key, value;
jsonValue = function(attr) {
if (Em.isArray(attr)) {
return attr.map(jsonValue);
}
if (App.Jsonable.detect(attr)) {
return attr.getJson();
}
return attr;
};
base = Em.isNone(this.get('jsonProperties')) ? this : this.getProperties(this.get('jsonProperties'));
json = {};
for (key in base) {
if (!hasProp.call(base, key)) continue;
value = base[key];
if (value === 'toString' || Em.typeOf(value) === 'function') {
continue;
}
json[key] = jsonValue(value);
}
return json;
}
});

Ember Data Model's object counts with a toJSON method which optionally receives an plain object with includeId property used to convert an Ember Data Model into a JSON with the properties of the model.
https://api.emberjs.com/ember-data/2.10/classes/DS.Model/methods/toJSON?anchor=toJSON
You can use it as follows:
const objects = models.map((model) => model.toJSON({ includeId: true }));
Hope it helps. Enjoy!

I have:
fixed and simplified code
added circular reference prevention
added use of get of value
removed all of the default properties of an empty component
//Modified by Shimon Doodkin
//Based on answers of: #leo, #pangratz, #kevin-pauli, #Klaus
//http://stackoverflow.com/questions/8669340
App.Jsonable = Em.Mixin.create({
getJson : function (keysToSkip, visited) {
//getJson() called with no arguments,
// they are to pass on values during recursion.
if (!keysToSkip)
keysToSkip = Object.keys(Ember.Component.create());
if (!visited)
visited = [];
visited.push(this);
var getIsFunction;
var jsonValue = function (attr, key, obj) {
if (Em.isArray(attr))
return attr.map(jsonValue);
if (App.Jsonable.detect(attr))
return attr.getJson(keysToSkip, visited);
return getIsFunction?obj.get(key):attr;
};
var base;
if (!Em.isNone(this.get('jsonProperties')))
base = this.getProperties(this.get('jsonProperties'));
else
base = this;
getIsFunction=Em.typeOf(base.get) === 'function';
var json = {};
var hasProp = Object.prototype.hasOwnProperty;
for (var key in base) {
if (!hasProp.call(base, key) || keysToSkip.indexOf(key) != -1)
continue;
var value = base[key];
// there are usual circular references
// on keys: ownerView, controller, context === base
if ( value === base ||
value === 'toString' ||
Em.typeOf(value) === 'function')
continue;
// optional, works also without this,
// the rule above if value === base covers the usual case
if (visited.indexOf(value) != -1)
continue;
json[key] = jsonValue(value, key, base);
}
visited.pop();
return json;
}
});
/*
example:
DeliveryInfoInput = Ember.Object.extend(App.Jsonable,{
jsonProperties: ["title","value","name"], //Optionally specify properties for json
title:"",
value:"",
input:false,
textarea:false,
size:22,
rows:"",
name:"",
hint:""
})
*/

Ember.js appears to have a JSON library available. I hopped into a console (Firebug) on one the Todos example and the following worked for me:
hash = { test:4 }
JSON.stringify(hash)
So you should be able to just change your line to
App.io.emit('node', { node:JSON.stringify(hash) })

unique object identifier in javascript

I need to do some experiment and I need to know some kind of unique identifier for objects in javascript, so I can see if they are the same. I don't want to use equality operators, I need something like the id() function in python.
Does something like this exist ?

Update My original answer below was written 6 years ago in a style befitting the times and my understanding. In response to some conversation in the comments, a more modern approach to this is as follows:
(function() {
if ( typeof Object.id != "undefined" ) return;
var id = 0;
Object.id = function(o) {
if ( typeof o.__uniqueid != "undefined" ) {
return o.__uniqueid;
}
Object.defineProperty(o, "__uniqueid", {
value: ++id,
enumerable: false,
// This could go either way, depending on your
// interpretation of what an "id" is
writable: false
});
return o.__uniqueid;
};
})();
var obj = { a: 1, b: 1 };
console.log(Object.id(obj));
console.log(Object.id([]));
console.log(Object.id({}));
console.log(Object.id(/./));
console.log(Object.id(function() {}));
for (var k in obj) {
if (obj.hasOwnProperty(k)) {
console.log(k);
}
}
// Logged keys are `a` and `b`
If you have archaic browser requirements, check here for browser compatibility for Object.defineProperty.
The original answer is kept below (instead of just in the change history) because I think the comparison is valuable.
You can give the following a spin. This also gives you the option to explicitly set an object's ID in its constructor or elsewhere.
(function() {
if ( typeof Object.prototype.uniqueId == "undefined" ) {
var id = 0;
Object.prototype.uniqueId = function() {
if ( typeof this.__uniqueid == "undefined" ) {
this.__uniqueid = ++id;
}
return this.__uniqueid;
};
}
})();
var obj1 = {};
var obj2 = new Object();
console.log(obj1.uniqueId());
console.log(obj2.uniqueId());
console.log([].uniqueId());
console.log({}.uniqueId());
console.log(/./.uniqueId());
console.log((function() {}).uniqueId());
Take care to make sure that whatever member you use to internally store the unique ID doesn't collide with another automatically created member name.

So far as my observation goes, any answer posted here can have unexpected side effects.
In ES2015-compatible enviroment, you can avoid any side effects by using WeakMap.
const id = (() => {
let currentId = 0;
const map = new WeakMap();
return (object) => {
if (!map.has(object)) {
map.set(object, ++currentId);
}
return map.get(object);
};
})();
id({}); //=> 1

Latest browsers provide a cleaner method for extending Object.prototype. This code will make the property hidden from property enumeration (for p in o)
For the browsers that implement defineProperty, you can implement uniqueId property like this:
(function() {
var id_counter = 1;
Object.defineProperty(Object.prototype, "__uniqueId", {
writable: true
});
Object.defineProperty(Object.prototype, "uniqueId", {
get: function() {
if (this.__uniqueId == undefined)
this.__uniqueId = id_counter++;
return this.__uniqueId;
}
});
}());
For details, see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/defineProperty

Actually, you don't need to modify the object prototype and add a function there. The following should work well for your purpose.
var __next_objid=1;
function objectId(obj) {
if (obj==null) return null;
if (obj.__obj_id==null) obj.__obj_id=__next_objid++;
return obj.__obj_id;
}

For browsers implementing the Object.defineProperty() method, the code below generates and returns a function that you can bind to any object you own.
This approach has the advantage of not extending Object.prototype.
The code works by checking if the given object has a __objectID__ property, and by defining it as a hidden (non-enumerable) read-only property if not.
So it is safe against any attempt to change or redefine the read-only obj.__objectID__ property after it has been defined, and consistently throws a nice error instead of silently fail.
Finally, in the quite extreme case where some other code would already have defined __objectID__ on a given object, this value would simply be returned.
var getObjectID = (function () {
var id = 0; // Private ID counter
return function (obj) {
if(obj.hasOwnProperty("__objectID__")) {
return obj.__objectID__;
} else {
++id;
Object.defineProperty(obj, "__objectID__", {
/*
* Explicitly sets these two attribute values to false,
* although they are false by default.
*/
"configurable" : false,
"enumerable" : false,
/*
* This closure guarantees that different objects
* will not share the same id variable.
*/
"get" : (function (__objectID__) {
return function () { return __objectID__; };
})(id),
"set" : function () {
throw new Error("Sorry, but 'obj.__objectID__' is read-only!");
}
});
return obj.__objectID__;
}
};
})();

Typescript version of #justin answer, ES6 compatible, using Symbols to prevent any key collision and added into the global Object.id for convenience. Just copy paste the code below, or put it into an ObjecId.ts file you will import.
(enableObjectID)();
declare global {
interface ObjectConstructor {
id: (object: any) => number;
}
}
const uniqueId: symbol = Symbol('The unique id of an object');
export function enableObjectID(): void {
if (typeof Object['id'] !== 'undefined') {
return;
}
let id: number = 0;
Object['id'] = (object: any) => {
const hasUniqueId: boolean = !!object[uniqueId];
if (!hasUniqueId) {
object[uniqueId] = ++id;
}
return object[uniqueId];
};
}
Example of usage:
console.log(Object.id(myObject));

jQuery code uses it's own data() method as such id.
var id = $.data(object);
At the backstage method data creates a very special field in object called "jQuery" + now() put there next id of a stream of unique ids like
id = elem[ expando ] = ++uuid;
I'd suggest you use the same method as John Resig obviously knows all there is about JavaScript and his method is based on all that knowledge.

For the purpose of comparing two objects, the simplest way to do this would be to add a unique property to one of the objects at the time you need to compare the objects, check if the property exists in the other and then remove it again. This saves overriding prototypes.
function isSameObject(objectA, objectB) {
unique_ref = "unique_id_" + performance.now();
objectA[unique_ref] = true;
isSame = objectB.hasOwnProperty(unique_ref);
delete objectA[unique_ref];
return isSame;
}
object1 = {something:true};
object2 = {something:true};
object3 = object1;
console.log(isSameObject(object1, object2)); //false
console.log(isSameObject(object1, object3)); //true

I faced the same problem and here's the solution I implemented with ES6
code
let id = 0; // This is a kind of global variable accessible for every instance
class Animal {
constructor(name){
this.name = name;
this.id = id++;
}
foo(){}
// Executes some cool stuff
}
cat = new Animal("Catty");
console.log(cat.id) // 1

I've used code like this, which will cause Objects to stringify with unique strings:
Object.prototype.__defineGetter__('__id__', function () {
var gid = 0;
return function(){
var id = gid++;
this.__proto__ = {
__proto__: this.__proto__,
get __id__(){ return id }
};
return id;
}
}.call() );
Object.prototype.toString = function () {
return '[Object ' + this.__id__ + ']';
};
the __proto__ bits are to keep the __id__ getter from showing up in the object. this has been only tested in firefox.

Notwithstanding the advice not to modify Object.prototype, this can still be really useful for testing, within a limited scope. The author of the accepted answer changed it, but is still setting Object.id, which doesn't make sense to me. Here's a snippet that does the job:
// Generates a unique, read-only id for an object.
// The _uid is generated for the object the first time it's accessed.
(function() {
var id = 0;
Object.defineProperty(Object.prototype, '_uid', {
// The prototype getter sets up a property on the instance. Because
// the new instance-prop masks this one, we know this will only ever
// be called at most once for any given object.
get: function () {
Object.defineProperty(this, '_uid', {
value: id++,
writable: false,
enumerable: false,
});
return this._uid;
},
enumerable: false,
});
})();
function assert(p) { if (!p) throw Error('Not!'); }
var obj = {};
assert(obj._uid == 0);
assert({}._uid == 1);
assert([]._uid == 2);
assert(obj._uid == 0); // still

This one will calculate a HashCode for each object, optimized for string, number and virtually anything that has a getHashCode function. For the rest it assigns a new reference number.
(function() {
var __gRefID = 0;
window.getHashCode = function(ref)
{
if (ref == null) { throw Error("Unable to calculate HashCode on a null reference"); }
// already cached reference id
if (ref.hasOwnProperty("__refID")) { return ref["__refID"]; }
// numbers are already hashcodes
if (typeof ref === "number") { return ref; }
// strings are immutable, so we need to calculate this every time
if (typeof ref === "string")
{
var hash = 0, i, chr;
for (i = 0; i < ref.length; i++) {
chr = ref.charCodeAt(i);
hash = ((hash << 5) - hash) + chr;
hash |= 0;
}
return hash;
}
// virtual call
if (typeof ref.getHashCode === "function") { return ref.getHashCode(); }
// generate and return a new reference id
return (ref["__refID"] = "ref" + __gRefID++);
}
})();

If you came here because you deal with class instances like me you can use static vars/methods to reference instances by a custom unique id:
class Person {
constructor( name ) {
this.name = name;
this.id = Person.ix++;
Person.stack[ this.id ] = this;
}
}
Person.ix = 0;
Person.stack = {};
Person.byId = id => Person.stack[ id ];
let store = {};
store[ new Person( "joe" ).id ] = true;
store[ new Person( "tim" ).id ] = true;
for( let id in store ) {
console.log( Person.byId( id ).name );
}

Here's a variant of Justin Johnson's answer that provides a scalability benefit when you are creating billions of objects for which you want the ID.
Specifically, rather than solely using a 1-up counter (that might overflow the representational limits of Number, and can't be cycled without risking reusing an ID), we register the object and its newly generated ID with a FinalizationRegistry, such that, at some point after the object is garbage collected, the ID is returned to a freelist for reuse by a newly created object (Python's id function can also return the same ID for multiple objects, so long as the existence of the two objects does not overlap in time).
Limitations:
It only works on objects, not JS primitives (this is somewhat reasonable; unlike Python, where everything is an object, JS primitives typically aren't, and the id function logically only works on objects, since primitives need not "exist" in any reasonably identifiable way).
If the code creates (without discarding) billions of objects, asks for their IDs, then releases them all at once and never asks for an ID again, the recovered IDs in the freelist constitute a memory leak of sorts. Hopefully the JS optimizer stores them efficiently, so the cost remains a small fraction of what the objects themselves cost, but it's still a cost. In cases where objects with IDs are regularly created and destroyed, the wasted memory is roughly tied to the maximum number of such ID-ed objects in existence at any given point in time.
If those limitations aren't a problem though, this works fairly well. I modified the testing code a bit to hand control back to the event loop (and hopefully the garbage collector) now and again while creating 10M garbage objects to ID, and on my browser, nearly half the object IDs get reclaimed for reuse; the final loop making five objects and IDing them produces IDs just above 1M, when over 2M objects had IDs generated at some point. In a realistic scenario with meaningful code executing and real async usage I'd expect better results simply because there would be more opportunities for the finalization registry to perform cleanup.
async function sleep(ms) {
await _sleep(ms);
}
function _sleep(ms) {
return new Promise((resolve) => setTimeout(resolve, ms));
}
(function() {
if ( typeof Object.id != "undefined" ) return;
var freelist = []; // Stores previously used IDs for reuse when an object with
// an ID is garbage collected, so creating and dropping billions
// of objects doesn't consume all available IDs
const registry = new FinalizationRegistry((freeid) => {
freelist.push(freeid);
});
var id = 0;
Object.id = function(o) {
if ( typeof o.__uniqueid != "undefined" ) {
return o.__uniqueid;
}
Object.defineProperty(o, "__uniqueid", {
value: freelist.length ? freelist.pop() : ++id,
enumerable: false,
// This could go either way, depending on your
// interpretation of what an "id" is
writable: false
});
registry.register(o, o.__uniqueid); // Sometime after o is collected, its ID
// will be reclaimed for use by a new object
return o.__uniqueid;
};
})();
var obj = { a: 1, b: 1 };
console.log(Object.id(obj));
console.log(Object.id([]));
console.log(Object.id({}));
console.log(Object.id(/./));
var idsum = 0; // So we do something real to prevent optimizing out code
// Make a ton of temporary objects with IDs, handing control back to the event loop
// every once in a while to (hopefully) see some IDs returned to the pool
for (var i = 0; i < 1000000; ++i) {
idsum += Object.id({c: i});
}
sleep(10).then(() => {
console.log(Object.id(function() { console.log("Hey"); }));
for (var i = 1000000; i < 2000000; ++i) {
idsum += Object.id({c: i});
}
console.log(Object.id(function() { console.log("There"); }));
sleep(10).then(() => {
for (var i = 0; i < 5; ++i) {
console.log(Object.id([i]));
}
console.log(idsum);
});
});
for (var k in obj) {
if (obj.hasOwnProperty(k)) {
console.log(k);
}
}
// Logged keys are `a` and `b`

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