commons.js

// Declare shorthand functions. Sharing these declarations across modules
// improves both consistency and minification. Unused declarations are
// dropped by the tree shaking process.

// we capture these, not just for brevity, but for security. If any code
// modifies Object to change what 'assign' points to, the Realm shim would be
// corrupted.

export const {
  assign,
  create,
  freeze,
  defineProperties, // Object.defineProperty is allowed to fail
  // silentlty, use Object.defineProperties instead.
  getOwnPropertyDescriptor,
  getOwnPropertyDescriptors,
  getOwnPropertyNames,
  getPrototypeOf,
  setPrototypeOf
} = Object;

export const {
  apply,
  ownKeys // Reflect.ownKeys includes Symbols and unenumerables,
  // unlike Object.keys()
} = Reflect;

/**
 * uncurryThis() See
 * http://wiki.ecmascript.org/doku.php?id=conventions:safe_meta_programming
 * which only lives at
 * http://web.archive.org/web/20160805225710/http://wiki.ecmascript.org/doku.php?id=conventions:safe_meta_programming
 *
 * Performance:
 * 1. The native call is about 10x faster on FF than chrome
 * 2. The version using Function.bind() is about 100x slower on FF,
 *    equal on chrome, 2x slower on Safari
 * 3. The version using a spread and Reflect.apply() is about 10x
 *    slower on FF, equal on chrome, 2x slower on Safari
 *
 * const bind = Function.prototype.bind;
 * const uncurryThis = bind.bind(bind.call);
 */
const uncurryThis = fn => (thisArg, ...args) => apply(fn, thisArg, args);

// We also capture these for security: changes to Array.prototype after the
// Realm shim runs shouldn't affect subsequent Realm operations.
export const objectHasOwnProperty = uncurryThis(
    Object.prototype.hasOwnProperty
  ),
  arrayForEach = uncurryThis(Array.prototype.forEach),
  arrayFilter = uncurryThis(Array.prototype.filter),
  arrayPush = uncurryThis(Array.prototype.push),
  arrayPop = uncurryThis(Array.prototype.pop),
  arrayJoin = uncurryThis(Array.prototype.join),
  arrayConcat = uncurryThis(Array.prototype.concat),
  regexpTest = uncurryThis(RegExp.prototype.test),
  stringMatch = uncurryThis(String.prototype.match),
  stringIncludes = uncurryThis(String.prototype.includes);