JavaScript에서 JSON 문자열을 특정 객체 프로토 타입으로 구문 분석

JavaScript에서 JSON 문자열을 특정 객체 프로토 타입으로 구문 분석

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JSON 문자열을 구문 분석하여 JavaScript 객체로 변환하는 방법을 알고 있습니다. JSON.parse()최신 브라우저 (및 IE9 +)에서 사용할 수 있습니다 .

훌륭하지만 JavaScript 객체를 특정 JavaScript 객체 (예 : 특정 프로토 타입)로 전환하려면 어떻게해야합니까?

예를 들어, 다음이 있다고 가정하십시오.

function Foo()
{
   this.a = 3;
   this.b = 2;
   this.test = function() {return this.a*this.b;};
}
var fooObj = new Foo();
alert(fooObj.test() ); //Prints 6
var fooJSON = JSON.parse({"a":4, "b": 3});
//Something to convert fooJSON into a Foo Object
//....... (this is what I am missing)
alert(fooJSON.test() ); //Prints 12

다시 한 번 JSON 문자열을 일반 JavaScript 객체로 변환하는 방법이 궁금하지 않습니다. JSON 문자열을 "Foo"개체로 변환하는 방법을 알고 싶습니다. 즉, 내 객체에는 이제 함수 'test'와 속성 'a'와 'b'가 있어야합니다.

업데이트 약간의 연구를 한 후, 나는 이것을 생각했습니다 ...

Object.cast = function cast(rawObj, constructor)
{
    var obj = new constructor();
    for(var i in rawObj)
        obj[i] = rawObj[i];
    return obj;
}
var fooJSON = Object.cast({"a":4, "b": 3}, Foo);

작동합니까?

업데이트 2017 년 5 월 :이 작업을 수행하는 "현대적인"방법은 via Object.assign이지만 IE 11 또는 이전 Android 브라우저에서는이 기능을 사용할 수 없습니다.

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현재 답변에는 많은 수작업 또는 라이브러리 코드가 포함되어 있습니다. 필요하지 않습니다.

1. JSON.parse('{"a":1}')일반 객체를 만드는 데 사용 합니다.

2. 표준화 된 기능 중 하나를 사용하여 프로토 타입을 설정하십시오.

   • Object.assign(new Foo, { a: 1 })
   • Object.setPrototypeOf({ a: 1 }, Foo.prototype)

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아래 예를 참조하십시오 (이 예는 기본 JSON 객체를 사용함). 변경 사항은 CAPITALS에 주석 처리됩니다.

function Foo(obj) // CONSTRUCTOR CAN BE OVERLOADED WITH AN OBJECT
{
    this.a = 3;
    this.b = 2;
    this.test = function() {return this.a*this.b;};

    // IF AN OBJECT WAS PASSED THEN INITIALISE PROPERTIES FROM THAT OBJECT
    for (var prop in obj) this[prop] = obj[prop];
}

var fooObj = new Foo();
alert(fooObj.test() ); //Prints 6

// INITIALISE A NEW FOO AND PASS THE PARSED JSON OBJECT TO IT
var fooJSON = new Foo(JSON.parse('{"a":4,"b":3}'));

alert(fooJSON.test() ); //Prints 12

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JSON 직렬화 / 역 직렬화 기능을 추가 하시겠습니까? 그런 다음 이것을보십시오 :

당신 은 이것을 달성하고 싶습니다 :

toJson ()은 일반적인 메소드입니다.
fromJson ()은 정적 메소드입니다.

구현 :

var Book = function (title, author, isbn, price, stock){
    this.title = title;
    this.author = author;
    this.isbn = isbn;
    this.price = price;
    this.stock = stock;

    this.toJson = function (){
        return ("{" +
            "\"title\":\"" + this.title + "\"," +
            "\"author\":\"" + this.author + "\"," +
            "\"isbn\":\"" + this.isbn + "\"," +
            "\"price\":" + this.price + "," +
            "\"stock\":" + this.stock +
        "}");
    };
};

Book.fromJson = function (json){
    var obj = JSON.parse (json);
    return new Book (obj.title, obj.author, obj.isbn, obj.price, obj.stock);
};

사용법 :

var book = new Book ("t", "a", "i", 10, 10);
var json = book.toJson ();
alert (json); //prints: {"title":"t","author":"a","isbn":"i","price":10,"stock":10}

var book = Book.fromJson (json);
alert (book.title); //prints: t

Note: If you want you can change all property definitions like this.title, this.author, etc by var title, var author, etc. and add getters to them to accomplish the UML definition.

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A blog post that I found useful: Understanding JavaScript Prototypes

You can mess with the __proto__ property of the Object.

var fooJSON = jQuery.parseJSON({"a":4, "b": 3});
fooJSON.__proto__ = Foo.prototype;

This allows fooJSON to inherit the Foo prototype.

I don't think this works in IE, though... at least from what I've read.

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Am I missing something in the question or why else nobody mentioned reviver parameter of JSON.parse since 2011?

Here is simplistic code for solution that works: https://jsfiddle.net/Ldr2utrr/

function Foo()
{
   this.a = 3;
   this.b = 2;
   this.test = function() {return this.a*this.b;};
}


var fooObj = new Foo();
alert(fooObj.test() ); //Prints 6
var fooJSON = JSON.parse(`{"a":4, "b": 3}`, function(key,value){
if(key!=="") return value; //logic of course should be more complex for handling nested objects etc.
  let res = new Foo();
  res.a = value.a;
  res.b = value.b;
  return res;
});
// Here you already get Foo object back
alert(fooJSON.test() ); //Prints 12

PS: Your question is confusing: >>That's great, but how can I take that JavaScript Object and turn it into a particular JavaScript Object (i.e. with a certain prototype)? contradicts to the title, where you ask about JSON parsing, but the quoted paragraph asks about JS runtime object prototype replacement.

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For the sake of completeness, here's a simple one-liner I ended up with (I had no need checking for non-Foo-properties):

var Foo = function(){ this.bar = 1; };

// angular version
var foo = angular.extend(new Foo(), angular.fromJson('{ "bar" : 2 }'));

// jquery version
var foo = jQuery.extend(new Foo(), jQuery.parseJSON('{ "bar" : 3 }'));

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An alternate approach could be using Object.create. As first argument, you pass the prototype, and for the second one you pass a map of property names to descriptors:

function SomeConstructor() {
  
};

SomeConstructor.prototype = {
  doStuff: function() {
      console.log("Some stuff"); 
  }
};

var jsonText = '{ "text": "hello wrold" }';
var deserialized = JSON.parse(jsonText);

// This will build a property to descriptor map
// required for #2 argument of Object.create
var descriptors = Object.keys(deserialized)
  .reduce(function(result, property) {
    result[property] = Object.getOwnPropertyDescriptor(deserialized, property);
  }, {});

var obj = Object.create(SomeConstructor.prototype, descriptors);

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I created a package called json-dry. It supports (circular) references and also class instances.

You have to define 2 new methods in your class (toDry on the prototype and unDry as a static method), register the class (Dry.registerClass), and off you go.

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I've combined the solutions that I was able to find and compiled it into a generic one that can automatically parse a custom object and all it's fields recursively so you can use prototype methods after deserialization.

One assumption is that you defined a special filed that indicates it's type in every object you want to apply it's type automatically (this.__type in the example).

function Msg(data) {
    //... your init code
    this.data = data //can be another object or an array of objects of custom types. 
                     //If those objects defines `this.__type', their types will be assigned automatically as well
    this.__type = "Msg"; // <- store the object's type to assign it automatically
}

Msg.prototype = {
    createErrorMsg: function(errorMsg){
        return new Msg(0, null, errorMsg)
    },
    isSuccess: function(){
        return this.errorMsg == null;
    }
}

usage:

var responseMsg = //json string of Msg object received;
responseMsg = assignType(responseMsg);

if(responseMsg.isSuccess()){ // isSuccess() is now available
      //furhter logic
      //...
}

Type assignment function (it work recursively to assign types to any nested objects; it also iterates through arrays to find any suitable objects):

function assignType(object){
    if(object && typeof(object) === 'object' && window[object.__type]) {
        object = assignTypeRecursion(object.__type, object);
    }
    return object;
}

function assignTypeRecursion(type, object){
    for (var key in object) {
        if (object.hasOwnProperty(key)) {
            var obj = object[key];
            if(Array.isArray(obj)){
                 for(var i = 0; i < obj.length; ++i){
                     var arrItem = obj[i];
                     if(arrItem && typeof(arrItem) === 'object' && window[arrItem.__type]) {
                         obj[i] = assignTypeRecursion(arrItem.__type, arrItem);
                     }
                 }
            } else  if(obj && typeof(obj) === 'object' && window[obj.__type]) {
                object[key] = assignTypeRecursion(obj.__type, obj);
            }
        }
    }
    return Object.assign(new window[type](), object);
}

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I like adding an optional argument to the constructor and calling Object.assign(this, obj), then handling any properties that are objects or arrays of objects themselves:

constructor(obj) {
    if (obj != null) {
        Object.assign(this, obj);
        if (this.ingredients != null) {
            this.ingredients = this.ingredients.map(x => new Ingredient(x));
        }
    }
}

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While, this is not technically what you want, if you know before hand the type of object you want to handle you can use the call/apply methods of the prototype of your known object.

you can change this

alert(fooJSON.test() ); //Prints 12

to this

alert(Foo.prototype.test.call(fooJSON); //Prints 12

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Olivers answers is very clear, but if you are looking for a solution in angular js, I have written a nice module called Angular-jsClass which does this ease, having objects defined in litaral notation is always bad when you are aiming to a big project but saying that developers face problem which exactly BMiner said, how to serialize a json to prototype or constructor notation objects

var jone = new Student();
jone.populate(jsonString); // populate Student class with Json string
console.log(jone.getName()); // Student Object is ready to use

https://github.com/imalhasaranga/Angular-JSClass

참고 URL : https://stackoverflow.com/questions/5873624/parse-json-string-into-a-particular-object-prototype-in-javascript