javascript - A shorter class initialisation in ECMAScript 6

Question

Every time I create some class, I need to do the same boring procedure:

class Something {
  constructor(param1, param2, param3, ...) {
    this.param1 = param1;
    this.param2 = param2;
    this.param3 = param3;
    ...
  }
}

Is there any way to make it more elegant and shorter? I use Babel, so some ES7 experimental features are allowed. Maybe decorators can help?

Answer 1

You can use Object.assign:

class Something {
  constructor(param1, param2, param3) {
    Object.assign(this, {param1, param2, param3});
  }
}

It's an ES2015 (aka ES6) feature that assigns the own enumerable properties of one or more source objects to a target object.

Granted, you have to write the arg names twice, but at least it's a lot shorter, and if you establish this as your idiom, it handles it well when you have arguments you do want on the instance and others you don't, e.g.:

class Something {
  constructor(param1, param2, param3) {
    Object.assign(this, {param1, param3});
    // ...do something with param2, since we're not keeping it as a property...
  }
}

Example: (live copy on Babel's REPL):

class Something {
  constructor(param1, param2, param3) {
    Object.assign(this, {param1, param2, param3});
  }
}
let s = new Something('a', 'b', 'c');
console.log(s.param1);
console.log(s.param2);
console.log(s.param3);

Output:

a
b
c