ie8 不支持 document.getElementsByClassName

在使用  document.getElementsByClassName 前加上

　　

   if (!document.getElementsByClassName) {

                document.getElementsByClassName = function (className, element) {

                    var children = (element || document).getElementsByTagName('*');

                    var elements = new Array();

                    for (var i = 0; i < children.length; i++) {

                        var child = children[i];

                        var classNames = child.className.split(' ');

                        for (var j = 0; j < classNames.length; j++) {

                            if (classNames[j] == className) {

                                elements.push(child);

                                break;

                            }

                        }

                    }

                    return elements;

                };

            }

 

ok！