shim.js

/**
 * Shim for "fixing" IE's lack of support (IE < 9) for applying slice
 * on host objects like NamedNodeMap, NodeList, and HTMLCollection
 * (technically, since host objects have been implementation-dependent,
 * at least before ES6, IE hasn't needed to work this way).
 * Also works on strings, fixes IE < 9 to allow an explicit undefined
 * for the 2nd argument (as in Firefox), and prevents errors when
 * called on other DOM objects.
 */
(function () {
    'use strict';
    var _slice = Array.prototype.slice;

    try {
        // Can't be used with DOM elements in IE < 9
        _slice.call(document.documentElement);
    } catch (e) { // Fails in IE < 9
        // This will work for genuine arrays, array-like objects, 
        // NamedNodeMap (attributes, entities, notations),
        // NodeList (e.g., getElementsByTagName), HTMLCollection (e.g., childNodes),
        // and will not fail on other DOM objects (as do DOM elements in IE < 9)
        var clone = function (arraylike, isStr, begin, end) {
            var i, cloned = [],
                size, len = arraylike.length;
            var start = begin || 0;
            start = (start >= 0) ? start: len +  start;
            var upTo = (end) ? end : len;
            if (end < 0) {
                upTo = len + end;
            }
            size = upTo - start;
            if (size > 0) {
                cloned = new Array(size);
                if (isStr) {
                    for (i = 0; i < cloned.length; i++) {
                        cloned[i] = arraylike.charAt(start + i);
                    }
                } else {
                    for (i = 0; i < cloned.length; i++) {
                        cloned[i] = arraylike[start + i];
                    }
                }
            }
            return cloned;
        };

        Array.prototype.slice = function (begin, end) {
            return (Object.prototype.toString.call(this) === '[object Array]') ?
                _slice.call(this, begin, end || this.length) :
                clone(this, this.charAt, begin, end);
        };
    }
}());