core-js/internals/async-iterator-prototype.js

'use strict';
var global = require('../internals/global');
var shared = require('../internals/shared-store');
var isCallable = require('../internals/is-callable');
var create = require('../internals/object-create');
var getPrototypeOf = require('../internals/object-get-prototype-of');
var defineBuiltIn = require('../internals/define-built-in');
var wellKnownSymbol = require('../internals/well-known-symbol');
var IS_PURE = require('../internals/is-pure');

var USE_FUNCTION_CONSTRUCTOR = 'USE_FUNCTION_CONSTRUCTOR';
var ASYNC_ITERATOR = wellKnownSymbol('asyncIterator');
var AsyncIterator = global.AsyncIterator;
var PassedAsyncIteratorPrototype = shared.AsyncIteratorPrototype;
var AsyncIteratorPrototype, prototype;

if (PassedAsyncIteratorPrototype) {
  AsyncIteratorPrototype = PassedAsyncIteratorPrototype;
} else if (isCallable(AsyncIterator)) {
  AsyncIteratorPrototype = AsyncIterator.prototype;
} else if (shared[USE_FUNCTION_CONSTRUCTOR] || global[USE_FUNCTION_CONSTRUCTOR]) {
  try {
    // eslint-disable-next-line no-new-func -- we have no alternatives without usage of modern syntax
    prototype = getPrototypeOf(getPrototypeOf(getPrototypeOf(Function('return async function*(){}()')())));
    if (getPrototypeOf(prototype) === Object.prototype) AsyncIteratorPrototype = prototype;
  } catch (error) { /* empty */ }
}

if (!AsyncIteratorPrototype) AsyncIteratorPrototype = {};
else if (IS_PURE) AsyncIteratorPrototype = create(AsyncIteratorPrototype);

if (!isCallable(AsyncIteratorPrototype[ASYNC_ITERATOR])) {
  defineBuiltIn(AsyncIteratorPrototype, ASYNC_ITERATOR, function () {
    return this;
  });
}

module.exports = AsyncIteratorPrototype;