Is it possible to destructure instance/member variables in a JavaScript constructor?

Question

Is it possible to use destructuring assignment in a JavaScript class' constructor to assign the instance variables similar to how you can do it to normal variables?

The following example works:

var options = {one: 1, two: 2}; var {one, two} = options; console.log(one) //=> 1 console.log(two) //=> 2 

But I cannot get something like the following to work:

class Foo {   constructor(options) {     {this.one, this.two} = options;     // This doesn't parse correctly and wrapping in parentheses doesn't help   } }  var foo = new Foo({one: 1, two: 2}); console.log(foo.one) //=> I want this to output 1 console.log(foo.two) //=> I want this to output 2 

Answer 1

There are multiple ways of doing this. The first one uses destructuring only and assigns the properties of options to properties on this:

class Foo {   constructor(options) {     ({one: this.one, two: this.two} = options);     // Do something else with the other options here   } } 

The extra parentheses are needed, otherwise the JS engine might mistake the { ... } for an object literal or a block statement.

The second one uses Object.assign and destructuring:

class Foo {   constructor(options) {     const {one, two} = options;     Object.assign(this, {one, two});     // Do something else with the other options here   } } 

If you want to apply all your options to the instance, you could use Object.assign without destructuring:

class Foo {   constructor(options) {     Object.assign(this, options);   } }