index.js

/* Created by tommyZZM.OSX on 2017/1/14. */
"use strict";

const curry = require("fast-curry");

const Symbol = (typeof global.Symbol === "function"
  && typeof global.Symbol.iterator === "symbol") ? global.Symbol : function (key) {
  return key + "_" + Date.now() + "_" + ((Math.random() * 10).toFixed(2));
};

const KEY_ACCESSOR_VALUES = Symbol('accessorValues');
const KEY_ACCESSOR_VALUE_GETTERS = Symbol('accessorValueGetters');
const KEY_ACCESSOR_VALUE_SETTERS = Symbol('accessorValueSetters');

const OptimizedAccessors = {};

function getterOf(prop) {
  return function () {
    const self = this;
    const accessorValues = self[KEY_ACCESSOR_VALUES];
    const accessorValueGetters = self[KEY_ACCESSOR_VALUE_GETTERS];

    const lastValue = accessorValues[prop];
    const getter = accessorValueGetters[prop];

    return getter(lastValue, prop, self);
  }
}

function setterOf(prop) {
  return function (newValue) {
    const self = this;
    const accessorValues = self[KEY_ACCESSOR_VALUES];
    const accessorValueSetters = self[KEY_ACCESSOR_VALUE_SETTERS];

    const setter = accessorValueSetters[prop];
    let lastValue = accessorValues[prop];

    lastValue = setter(
      lastValue, newValue, prop, self
    );

    accessorValues[prop] = lastValue;
  }
}

const objectAssignProperties = curry(function (descriptor, properties, object) {

  const isOwnsGetter = typeof descriptor.get === "function";
  const isOwnsSetter = typeof descriptor.set === "function";
  const isOwnsGetterOrSetter = isOwnsGetter || isOwnsSetter;

  const get = descriptor.get;
  const set = descriptor.set;
  const isShareAccessor = Boolean(descriptor.shareAccessor);

  const _descriptor = Object.keys(descriptor)
    .reduce((_descriptor, key) => {
      if ( key === "get" || key === "set" ) {
        return _descriptor;
      }

      // Cannot both specify accessors and a value or writable attribute
      if ( key === "writable" && isOwnsGetterOrSetter ) {
        return _descriptor;
      }

      _descriptor[key] = descriptor[key];
      return _descriptor;
    }, {});

  if ( isOwnsGetterOrSetter && isShareAccessor ) {
    [
      KEY_ACCESSOR_VALUES,
      KEY_ACCESSOR_VALUE_GETTERS,
      KEY_ACCESSOR_VALUE_SETTERS
    ].forEach(key => {
      let descriptor = Object.getOwnPropertyDescriptor(
        object, key
      );

      if ( !descriptor ) {
        Object.defineProperty(object, key, {
          value: {},
          enumerable: false,
          configurable: false
        })
      }
    });
  }

  const accessorValues = object[KEY_ACCESSOR_VALUES];
  const accessorValueGetters = object[KEY_ACCESSOR_VALUE_GETTERS];
  const accessorValueSetters = object[KEY_ACCESSOR_VALUE_SETTERS];

  let propNames = Object.keys(properties);

  if (typeof Object.getOwnPropertySymbols === "function") {
    propNames.push.apply(propNames, Object.getOwnPropertySymbols(properties));
  }

  return Object.defineProperties(object, propNames
    .reduce((_properties, prop) => {
      let value = properties[prop];

      if ( isOwnsGetterOrSetter && isShareAccessor ) {
        accessorValues[prop] = value;
        accessorValueGetters[prop] = get;
        accessorValueSetters[prop] = set;
      }

      let accessor = [];

      if (isShareAccessor) {
        accessor = OptimizedAccessors[prop]
        if ( !accessor ) {
          accessor = [
            getterOf(prop),
            setterOf(prop)
          ];
          OptimizedAccessors[prop] = accessor;
        }
      } else {
        accessor = [
          _ => get(value, prop, this),
          (new_value) => value = set(value, new_value, prop, this)
        ];
      }

      let _descriptorValue = isOwnsGetterOrSetter ? Object.assign(
        isOwnsGetter ? {
          get: accessor[0]
        } : {},
        isOwnsSetter ? {
          set: accessor[1]
        } : {}
      ) : { value };

      _properties[prop] = Object.assign(
        {}, _descriptor, _descriptorValue
      );
      return _properties
    }, {}));
})

/**
 * @module object-assign-properties
 * @function
 */
module.exports = objectAssignProperties;