@kingjs/reflect.export-extension

Extend a type with a property and return a symbol whose debug name is derived from the module hosting the extension.

Usage

var assert = require('assert');
var exportExtension = require('@kingjs/reflect.export-extension');
var IIterable = require('@kingjs/i-iterable');

// Assume the package is `@kingjs/ex` with version `1.0.0`.
var name = 'Symbol(@kingjs/ex, 1.0.0)';

/**
 * Export an extension `Rename` on Function that renames the
 * Function.  
 */
var Rename = exportExtension(
  module,
  Function,
  function(name) {
    Object.defineProperty(
      this, 'name', { value: name }
    )
  }
)
assert(module.exports == Rename);
assert(Rename.toString() == name);
//assert(Function.prototype[Rename].name == name);

function foo() { }
foo[Rename]('bar');
assert(foo.name == 'bar');

/**
 * Export an extension `Rename` on Function that renames the
 * Function, but this time as an accessor. Looks weird but 
 * illustrates using an accessor.
 */
var Rename = exportExtension(
  module,
  Function, {
    set: function(name) {
      Object.defineProperty(
        this, 'name', { value: name }
      )
    }
  }
)
function foo() { }
foo[Rename] = 'bar';
assert(foo.name == 'bar');

/**
 * Export an extension on Any() IIterable which is an Interface
 * implemented by all types with a Symbol.iterator property.
 */
var Any = exportExtension(
  module,
  IIterable,
  function() {
    var iterator = this[Symbol.iterator]();
    iterator = iterator.next();
    return !iterator.done;
  }
)

// string implements IIterable
assert(''[Any]() == false)
assert('foo'[Any]() == true)

// array implements IIterable
assert([][Any]() == false)
assert([ 0 ][Any]() == true)

/**
 * If the `kingjs` shim has been run, then String and Array
 * also implement IEnumerable which allows for extending
 * IEnumerable to implement `None` like this:
 */
var IEnumerable = require('@kingjs/i-enumerable');
var IEnumerator = require('@kingjs/i-enumerator');
var None = exportExtension(
  module,
  IEnumerable,
  function() {
    var enumerator = this[IEnumerable.getEnumerator]();
    return !enumerator[IEnumerator.moveNext]();
  }
)

require('kingjs');
require('@kingjs/assert-shimmed');

// string implements IEnumerable when shimmed
assert(''[None]() == true)
assert('foo'[None]() == false)

// array implements IEnumerable when shimmed
assert([][None]() == true)
assert([ 0 ][None]() == false)

API

exportExtension(module, type, descriptor)

Parameters

• module: The module hosting the extension.
• type: The type being extended.
• descriptor: The descriptor describing the property.

  Returns

  Returns the symbol name of the property. The symbol is not registered. The symbol's debug name is the hosting module name and its version.

  Remarks

  If the type is an interface than all types implementing the interface are extended. Overloads are similar to those provided by @kingjs/reflect.define-property

Install

With npm installed, run

$ npm install @kingjs/reflect.export-extension

Dependencies