aimingoo / public-property

The proposal is an enhancement of public property.

Public property in class member definition

The proposal is an enhancement of public property of class definition syntax.

The proposal will implementation public keyword in class definition:

• Nothing NEW

  Concept cleanly. All the features are grammatical sugar, except that the public keyword is enabled.

The proposal is not tc39 officailly now but implemented at prepack-core with proposal-public-property (@here).

You could see more test case in this project (@here).

Table of Contents

• Public property in class member definition
  • Syntax design
  • Concepts
  • Implementation
  • Testcases
  • References
  • History

Syntax design

Key principle:

​ All the features of grammatical sugar can be implement base on existing.

1. using public define public property, or default

Ex:

class f {
  public data = 100;
  public static data = 200;
}

// equal
let f = class {};
let defaultAttr = { writable: true, enumerable: true, configurable: true };
Object.defineProperty(f.prototype, 'data', {value: 100, ...defaultAttr});
Object.defineProperty(f, 'data', {value: 200, ...defaultAttr});

case 2:

class f {
  public foo() {
    // enabled, can be remove `public`
  }

  // equal
  foo() {
  }
}

2. publish member from private scope

example, for private property:

class MyClass {
  private x = 100;
  public as x;
}

// equal
class MyClass {
  private x = 100;

  get x() {
    return x;
  }
  set x(v) {
    x = v;
  }
}

case 2, for protected property:

class MyClass {
  protected x = 100;
}

class MyClassEx extends MyClass {
  public as x; // accept
}

3. publish with alias

Ex:

class MyClass {
  protected x = 100;
}

class MyClassEx extends MyClass {
  public x as valueX;  // alias `valueX`
}

// equal
class MyClassEx extends MyClass {
  get valueX() {
    return x;
  }
  set valueX(v) {
    x = v;
  }
}

Concepts

The truth is "All the normal properties are published in JavaScript".

Implementation

Core rules:

• Can not publish a no-private member using public as syntax.
• Can not assignment initialization value when public as a member.

Key implementation steps:

• eta public keyword when evaluate definition item.
• make get and set method for "public [name] as <name>" grammatical.

Done.

Testcases

The proposal has full test case in repository, current syntax based.

# install test framework
> mkdir node_modules
> npm install fancy-test chai mocha --no-save
# test it
> mocha

# (OR)
> bash run.sh

References

• Objections to fields, especially the private field syntax
• The proposal should be rejected!
• My comments at #100

History

2019.09.11 initial release.