iteragain/dist/es5/arrayLike.js

Javascript Iterable/Iterator/Generator-function utilities.

import seekable from './seekable';
// TODO: possible add an overload for passing in a seekable to begin with, so that the maxLength param could be used.
/**
 * @description Creates a proxy object that allows for readonly array-like access to the elements of the input iterator. Some
 * important things to note are:
 * - `length` will always be the length of the internal cache, not the length of the final
 * iterated values.
 * - `Symbol.iterator` will always iterate over the entire input iterator, not just the cached values.
 * - Negative indices are allowed, and will seek backwards from the end of the internal cache.
 * @param arg The input iterator or iterable.
 */
export function arrayLike(arg) {
    var it = seekable(arg);
    // eslint-disable-next-line no-undef
    return new Proxy([], {
        get: function (target, prop) {
            if (prop === 'length')
                return it.elements.length;
            else if (prop === Symbol.iterator) {
                it.seek(0);
                return it[Symbol.iterator].bind(it);
            }
            else if (prop && prop in it.elements) {
                var value = target[prop];
                if (typeof value === 'function')
                    return value.bind(it.elements);
            }
            var index = Number(prop);
            if (!isNaN(index)) {
                it.seek(index);
                return it.next().value;
            }
            return undefined;
        },
        has: function (_, prop) {
            return prop in it.elements;
        },
        ownKeys: function () {
            return Object.keys(it.elements).concat('length');
        },
        getOwnPropertyDescriptor: function (_, prop) {
            return Object.getOwnPropertyDescriptor(it.elements, prop);
        },
        set: function (_, prop) {
            throw new TypeError("Cannot assign to read only property '".concat(prop.toString(), "' of ArrayLikeIterator."));
        },
        deleteProperty: function (_, prop) {
            throw new TypeError("Cannot delete property '".concat(prop.toString(), "' of ArrayLikeIterator."));
        },
        defineProperty: function (_, prop) {
            throw new TypeError("Cannot define property '".concat(prop.toString(), "' of ArrayLikeIterator."));
        },
    });
}
export default arrayLike;
//# sourceMappingURL=arrayLike.js.map