各种常见兼容代码

getstyle

var getStyle = function (elem, style) {
            return 'getComputedStyle' in window ?
                getComputedStyle(elem, null)[style] :
                function () {
                    style = style.replace(/-(w)/g, function ($, $1) {
                        return $1.toUpperCase();
                    });
                    var val = elem.currentStyle[style];

                    if (val === 'auto' && (style === "width" || style === "height")) {
                        var rect = elem.getBoundingClientRect();
                        if (style === "width") {
                            return rect.right - rect.left + 'px';
                        } else {
                            return rect.bottom - rect.top + 'px';
                        }
                    }
                    return val;
                }();
        };

        // 调用该方法
        var test = document.getElementById('test'),
            // 获取计算的宽度
            tWidth = getStyle(test, 'width');

 class操作

 function hasClass(obj, cls) {
　　　　　　　　　　//热皮球
                return obj.className.match(new RegExp('(\s|^)' + cls + '(\s|$)'));
            }

            function addClass(obj, cls) {
                if (!this.hasClass(obj, cls)) obj.className += " " + cls;
            }

            function removeClass(obj, cls) {
                if (hasClass(obj, cls)) {
                    var reg = new RegExp('(\s|^)' + cls + '(\s|$)');
                    obj.className = obj.className.replace(reg, ' ');
                }
            }

            function toggleClass(obj, cls) {
                if (hasClass(obj, cls)) {
                    removeClass(obj, cls);
                } else {
                    addClass(obj, cls);
                }
            }

            function toggleClassTest() {
                var obj = document.getElementById('test');
                toggleClass(obj, "testClass");
            }