A polyfill for the ParentNode interface

parent-node.js

(function() {
    var polyfill = function(prototype)
    {
        if (!('firstElementChild' in prototype)) {
            Object.defineProperty(prototype, 'firstElementChild', {
                get: function() {
                    var nodes = this.childNodes;
                    var length = nodes.length;
                    var current;
                    for (var i = 0; i < length; i++) {
                        current = nodes[i];
                        if (current.nodeType === 1) {
                            return current;
                        }
                    }
                    return null;
                }
            });
        }
        
        if (!('lastElementChild' in prototype)) {
            Object.defineProperty(prototype, 'lastElementChild', {
                get: function() {
                    var nodes = this.childNodes;
                    var length = nodes.length;
                    var current;
                    for (var i = length - 1; i > 0; i--) {
                        current = nodes[i];
                        if (current.nodeType === 1) {
                            return current;
                        }
                    }
                    return null;
                }
            });
        }

        if (!('childElementCount' in prototype)) {
            Object.defineProperty(prototype, 'childElementCount', {
                get: function() {
                    var nodes = this.childNodes;
                    var length = nodes.length;
                    var count = 0;
                    for (var i = 0; i < nodes.length; i++) {
                        if (nodes[i].nodeType === 1) {
                            count++;
                        }
                    }
                    return count;
                }
            });
        }

        if (!('children' in prototype)) {
            Object.defineProperty(prototype, 'children', {
                get: function() {
                    var nodes = this.childNodes;
                    var length = nodes.length;
                    var children = [];
                    var current;
                    for (var i = 0; i < nodes.length; i++) {
                        current = nodes[i];
                        if (current.nodeType === 1) {
                            children.push(current);
                        }
                    }
                    return children;
                }
            });
        }
    }

    polyfill(Element.prototype);
    polyfill(Document.prototype);
    polyfill(DocumentFragment.prototype);
})();

Thank you very much 😽

Oh, PhpStorm is nagging about some unused variables 😱 The variable length should be used in the for loop in childElementCount and children (or not at all) 😉