src/animation: Convert to es6 classes

[ianpurvis]

Supports #19986

[Mugen87]

@ianpurvis Do you mind resolving the merge conflicts?

[ianpurvis]

@Mugen87 Will do!

[ianpurvis]

Fyi, I discarded c4872f5 in light of #21293

[mrdoob]

Hah! I didn't know you could do new this() 🤓

[mrdoob]

Wait, I see you do new this.constructor a bit further down the file. What's the difference?

[ianpurvis]

Yeah! If you are constructing from a static method you can use this(), otherwise you have to use this.constructor()

class Foo {

  constructor(attributes) {
    Object.assign(this, attributes);
  }

  static create(attributes) {
    return new this(attributes);
  }

  clone() {
    return new this.constructor(this) ;
  }
}

class Bar extends Foo { }


const objects = [
 new Foo({ name: 'foo1' }),
 Foo.create({ name: 'foo2' }),
 new Foo({ name: 'foo3' }).clone(),
 new Bar({ name: 'bar1' }),
 Bar.create({ name: 'bar2' }),
 new Bar({ name: 'bar3' }).clone(),
]

for (const obj of objects) {
  console.log(obj);
}

Outputs -->

Foo { name: 'foo1' }
Foo { name: 'foo2' }
Foo { name: 'foo3' }
Bar { name: 'bar1' }
Bar { name: 'bar2' }
Bar { name: 'bar3' }

[mrdoob]

Dang. You know your stuff! 🙏

[mrdoob]

Apart from the new this and new this.constructor question, the PR seems good to go 👌

[ianpurvis]

Caught and fixed an issue in 9c437fd 👍

[mrdoob]

Thanks!