对象字面量构造函数

Question

I am looking for a way to modify an object that was defined by a literal without passing it into another function.

example:

let o = {a:1,b:2}
console.log(o.a===3)

i thought when i define an object using a literal the the Object constructor would be called, so i did override Object.prototype.constructor but it only gets called when i do new Object({a:1,b:2})

question in simpler terms can anyone make a=3 without passing the object o to a function or a proxy or using oa=3 or with keyword, where o is defined using an object literal?

Answer 1

Just do oa=3; and console log o :

 let o = {a:1,b:2}; oa=3; console.log(o);

Currently you are doing oa===3 which will return Boolean value instead of overwriting the value of property a .

You also cannot do oa=3 inside console.log() because oa=3 will return the assigned value which is 3 but it will still change the property a of o to 3 .

 let o = { a: 1, b: 2 }; //won't print o but changes oa to 3 console.log(oa = 3);

Answer 2

It's simply not possible.
There is no constructor of an object literal.
You can create objects in different ways:

• via an object literal or
• via a constructor function or
• via Object.create

Also, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer

Answer 3

question in simpler terms can anyone make a=3 without passing the object o to a function or a proxy?

  o.a = 3;

I am looking for a way to modify an object that was defined by a literal without passing it into another function.

Thats impossible, cause if it would be possible you could break every piece of javascript. And that would be terrible.

Oh wait, this is JS...

 with({ get o() { return { a: 3 }; }, set o(v) {} }) {

  o = {a:1,b:2};
  console.log(o.a===3) // true

 }

Answer 4

What you want to achieve could be done if oa holds a reference to the variable a - which unfortunately only works the way you'd like for variables that are passed by reference . Primitive types like String , Number and Boolean though, are passed by value .

Check the examples below:

 var a = 1; var o = { a: a }; a = 2; console.log(oa, a);

It also doesn't help to use an Object constructor like new Number() because that does return a reference to an object (which is passed by reference as you'd need), but assigning a new value to it reading the value still returns a primitive (which is, again, passed by value ):

 var a = new Number(1); var o = { a: a.valueOf() }; a = Number(2); console.log(oa, a);

If you pass something that is naturally passed by reference, your expectation is fulfilled:

 var a = [ 1 ] var o = { a: a } a[0] = 2 console.log(oa[0])