TypeScript - pass to constructor entire object -

i have class @ type script:

export class child {   name:string;   age:number; } 

i want force class instances have properties class declaration has.

for example, if firebase object:

myfirebaseservice.getchild(id).then(function(child){   var currentchild = new child(child); })  

so when object is: {name:"ben", color:"db"}, want result be:

currentchild = {"name":"ben"} 

becouse "color" not field of "child".

i tried this:

export class child {   name:string;   age:number;    constructor(tempchild:child = null) {     if (tempchild){       (var prop in tempchild) {         this[prop] = tempchild[prop];       }     }   } } 

but not help. "currentchild" of fields , attached them class instance.

(of course, can use following code:

export class child {   name:string;   age:number;    constructor(tempchild:child = null) {     if (tempchild){       this.nam  = tempchild.name;       this.age =tempchild.ageÏ;     }   } } 

, truth class has many fields, , want short code)

you don't have many choices here, because member definitions make in class before constructor aren't being translated javascript, compiler leaves them out:

class child {     name: string;     age: number;      constructor() {         this.name = "name";     } } 

compiles into:

var child = (function () {     function child() {         this.name = "name";     }     return child; }()); 

as can see, name member 1 there, , used when assigned to.

because need names of members in runtime, you'll need have them set aside, example in array:

class child {     private static members = ["name", "age"];      name: string;     age: number;      constructor(tempchild: child = null) {         if (tempchild) {             (var prop in tempchild) {                 if (child.members.indexof(props) >= 0) {                     this[prop] = tempchild[prop];                 }             }         }     } } 

this isn't comfortable work with, can use decorators.
example:

function member(cls: any, name: string) {     if (!cls.constructor.members) {         cls.constructor.members = [];     }      cls.constructor.members.push(name); }  function ismember(cls: any, name: string): boolean {     return cls.members[name] != null; }  class child {     @member     name: string;      @member     age: number;      constructor(tempchild: child = null) {         if (tempchild) {             (var prop in tempchild) {                 if (ismember(child, prop)) {                     this[prop] = tempchild[prop];                 }             }         }     } } 

(code in playground)

it's not tested, i'm not sure it's working, if decide go way it's of need.