JS ES6: Get parameters as an object with destructuring

Question

Is it possible to get the function's arguments as an object (in order to iterate on it) using destructuring?

function({a=1, b=2, c=3}={}) {
  // how to get {a:1, b:2, c:3}?
}

My goal here is to bind each parameter to this in a class constructor.

It is possible without destructuring:

class Test {
  constructor(args) {
    Object.assign(this, args);
  }
}

But I don't know how to simplify that:

class Test {
  constructor({a=1, b=2, c=3}={}) {
    this.a = a;
    this.b = b;
    this.c = c;
  }
}

let test = new Test();
// test.a = 1 
// test.b = 2 etc.

Answer 1

You can do this, using the shorthand form of object creation:

class Test {
  constructor({a=1, b=2, c=3}={}) {
    Object.assign(this, {a, b, c});
  }
}

Example:

 class Test { constructor({a=1, b=2, c=3}={}) { Object.assign(this, {a, b, c}); } } const t1 = new Test(); console.log("t1:", t1.a, t1.b, t1.c); const t2 = new Test({b: 42}); console.log("t2:", t2.a, t2.b, t2.c); 

---

Alternately, don't use destructuring, and use multiple arguments to Object.assign :

 class Test { constructor(options = {}) { Object.assign(this, Test.defaults, options); } } Test.defaults = {a: 1, b: 2, c: 3}; // Usage: const t1 = new Test(); console.log("t1:", t1.a, t1.b, t1.c); const t2 = new Test({b: 42}); console.log("t2:", t2.a, t2.b, t2.c); 

...and if you want any of those as discrete things you can reference by name, you can either just use this.a (and this.b and this.c ) to do it, or you can do:

let {a, b, c} = this;

...afterward and use those. (Just beware that assigning to the resulting a , b , and c won't update the object.)