Javascript es6 overrides static properties

Question

Try ES6 and try to create a class with static properties and a function for parsing. Then I want to extend the base parser for each different type that I am processing. Not sure what I am doing anti-pattern, but I can not override static properties.

This is my base parser

class Module {

  static name = 'Default Module'
  static version = {major:10000, minor: 10000}

  static checkVersion({majorVersion = 10000, minorVersion = 10000}) {
    if(this.version.major !== majorVersion || this.version.minor > minorVersion) {
      throw `${this.name} requires version ${this.version.major}.${this.version.minor} got ${majorVersion}.${minorVersion}`;
    }
  }

  static parse(data) {
    try {
      this.checkVersion(data);
      return this.internalParser(data);

    } catch (e) {
      throw e;
    }
  }

  static internalParser(data) {
    throw `${this.name} has no parser implemented`;
  }
}

And then I want to continue like this

class ExtendedModule extends Module {
  static name = 'Extended';
  static version = {major: 1, minor:0}

  static internalParser(data) {
    //Some stuff
  }
}

But when compiling in node with babel, I get

true; if ('value' in descriptor) descriptor.writable = true; Object.defineProp
                                                                    ^
TypeError: Cannot redefine property: name
    at Function.defineProperty (native)

Has anyone understood if this is possible or simply wrong?

Answer 1

- ( ), , :

class Foo {
    static name = 'foo';
}

function Foo(){}
Object.defineProperty(Foo, 'name', {
    configurable: true,
    writable: true
    value: 'foo'
});

, , . , , name, Foo. ES5 name configurable: false, , , , , TypeError: Cannot redefine property: name .

ES6 name configurable: true, , , , .

, . , , . , , innerParser - . .

Answer 2

getter :

class Module {
    static get name() { return "Default Module"; }
    static get version() { return {major:10000, minor: 10000}; }

    static parse() {
        console.log( this.name );
    }
}

class ExtendedModule extends Module {
    static get name() { return "Extended"; }
    static get version() { return {major:1, minor: 0}; }
}

ExtendedModule.parse();

BabelJS,

"use strict";

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

var Module = function () {
    function Module() {
        _classCallCheck(this, Module);
    }

    _createClass(Module, null, [{
        key: "parse",
        value: function parse() {
            console.log(this.name);
        }
    }, {
        key: "name",
        get: function get() {
            return "Default Module";
        }
    }, {
        key: "version",
        get: function get() {
            return { major: 10000, minor: 10000 };
        }
    }]);

    return Module;
}();

var ExtendedModule = function (_Module) {
    _inherits(ExtendedModule, _Module);

    function ExtendedModule() {
        _classCallCheck(this, ExtendedModule);

        return _possibleConstructorReturn(this, (ExtendedModule.__proto__ || Object.getPrototypeOf(ExtendedModule)).apply(this, arguments));
    }

    _createClass(ExtendedModule, null, [{
        key: "name",
        get: function get() {
            return "Extended";
        }
    }, {
        key: "version",
        get: function get() {
            return { major: 1, minor: 0 };
        }
    }]);

    return ExtendedModule;
}(Module);

ExtendedModule.parse();

,

Extended

JS.

• ES5-: https://jsfiddle.net/dwq698r8/
• ES6-: https://jsfiddle.net/yd8bf7am/