Field initializers

Jordan Harband ljharb at gmail.com
Sat Mar 18 18:04:27 UTC 2017


I'd think with the advent of private fields a much more common (and better)
use case would not involve creating publicly visible properties - how might
that work?

Perhaps this:
```js
class Foo {
  constructor(#x, #y) { }
}
```

On Sat, Mar 18, 2017 at 11:00 AM, just nobody <kingdaro at gmail.com> wrote:

> Inherited methods would inherit the same behavior, since this is just
> syntactic sugar after all.
> ```js
> class Point {
>   setPosition(this.x, this.y) {}
>
>   // same as
>   // setPosition(x, y) { this.x = x; this.y = y }
> }
>
> class Rectangle extends Point {
>   setSize(this.width, this.height) {}
>
>   // same as
>   // setSize(width, height) { this.width = width; this.height = height }
> }
>
> let rect = new Rectangle()
> rect.setPosition(0, 0)
> rect.setSize(50, 50)
> rect // { x: 0, y: 0, width: 50, height: 50 }
> ```
>
> On Sat, Mar 18, 2017 at 7:12 AM Michael J. Ryan <tracker1 at gmail.com>
> wrote:
>
>> Interesting concept... What about inheritance?
>>
>> --
>> Michael J. Ryan - tracker1 at gmail.com - http://tracker1.info
>>
>> Please excuse grammar errors and typos, as this message was sent from my
>> phone.
>>
>> On Mar 18, 2017 12:03 AM, "just nobody" <kingdaro at gmail.com> wrote:
>>
>> Would it be possible to have syntax like this? It's a feature supported
>> by other JS variants in some way (CoffeeScript, TS) that feels missing from
>> the spec. It's mainly useful as a convenient, terse way of setting
>> properties of an object on initialization.
>>
>> ```js
>> class Rectangle {
>>   constructor (this.x, this.y, this.width, this.height) {}
>>   setPosition(this.x, this.y) {}
>>   setSize(this.width, this.height) {}
>> }
>>
>> // equivalent to
>> class Rectangle {
>>   constructor (x, y, width, height) {
>>     this.x = x
>>     this.y = y
>>     this.width = width
>>     this.height = height
>>   }
>>
>>   // ...
>> }
>>
>> // for regular constructor functions as well
>> function Rectangle (this.x, this.y, this.width, this.height) {}
>> ```
>>
>> Deconstructing and argument defaults should all work similarly
>> ```js
>> function Point({ x: this.x, y: this.y }) {}
>> function Point(this.x = 0, this.y = 0) {}
>> function Point([this.x, this.y]) {}
>> ```
>>
>>
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>>
>>
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