source: frontend/node_modules/es-abstract/helpers/getIteratorMethod.js

'use strict';

var hasSymbols = require('has-symbols')();
var GetIntrinsic = require('get-intrinsic');
var callBound = require('call-bound');
var isString = require('is-string');

var $iterator = GetIntrinsic('%Symbol.iterator%', true);
var $stringSlice = callBound('String.prototype.slice');
var $String = GetIntrinsic('%String%');

var IsArray = require('./IsArray');

module.exports = function getIteratorMethod(ES, iterable) {
        var usingIterator;
        if (hasSymbols) {
                usingIterator = ES.GetMethod(iterable, $iterator);
        } else if (IsArray(iterable)) {
                usingIterator = function () {
                        var i = -1;
                        var arr = this;
                        return {
                                next: function () {
                                        i += 1;
                                        return {
                                                done: i >= arr.length,
                                                value: arr[i]
                                        };
                                }
                        };
                };
        } else if (isString(iterable)) {
                usingIterator = function () {
                        var i = 0;
                        return {
                                next: function () {
                                        var nextIndex = ES.AdvanceStringIndex($String(iterable), i, true);
                                        var value = $stringSlice(iterable, i, nextIndex);
                                        i = nextIndex;
                                        var done = nextIndex > iterable.length;
                                        return {
                                                done: done,
                                                value: done ? void undefined : value
                                        };
                                }
                        };
                };
        }
        return usingIterator;
};