没有jquery的时候，你看看这个

vjs

    var br = (function() {
        var ua = navigator.userAgent.toLowerCase();
        browser = {
            iPhone: /iphone/.test(ua),
            iPad: /ipad/.test(ua),
            iPod: /ipod/.test(ua),
            isLetv: /letv/.test(ua),
            Android: /android/.test(ua),
            AndroidPad: /android/.test(ua) && !/mobile/.test(ua),
            atwin: /win/.test(ua),
            opera: /opera/.test(ua),
            msie: /msie/.test(ua),
            firefox: /firefox/.test(ua),
            safari: /safari/.test(ua) && !/chrome/.test(ua),
            wph: /windows phone/.test(ua),
            ps: /playstation/.test(ua),
            uc: /ucbrowser|ucweb/.test(ua),
            xiaomi: /xiaomi/.test(ua),
            weixin: /MicroMessenger/i.test(ua),
            isLetvTv: function() {
                try {
                    return typeof LetvFish.getBrowserType == 'function';
                } catch (e) {
                    return false;
                }
            }
        };

        var rwebkit = /(webkit)[ \/]([\w.]+)/,
            ropera = /(opera)(?:.*version)?[ \/]([\w.]+)/,
            rmsie = /(msie) ([\w.]+)/,
            rmozilla = /(mozilla)(?:.*? rv:([\w.]+))?/;

        var match = rwebkit.exec(ua) ||
            ropera.exec(ua) ||
            rmsie.exec(ua) ||
            ua.indexOf("compatible") < 0 && rmozilla.exec(ua) || [];

        browser.version = match[2] || "0";
        return browser;
    })();
    var $js = (function() {
        var undefined, filter = [].filter,
            slice = [].slice,
            class2type = {},
            classSelectorRE = /^\.([\w-]+)$/,
            idSelectorRE = /^#([\w-]*)$/,
            tagSelectorRE = /^[\w-]+$/;

        var browser = br;

        /**
         *  @desc vjs框架入口，实现DOM选择器
         *
         */
        vjs = function(selector, context) {
            return new vjs.fn.init(selector, context);
        }

        vjs.isPC = false;

        var qsa = function(element, selector) {
            var found
            try {
                return (isDocument(element) && idSelectorRE.test(selector)) ?
                    ((found = element.getElementById(RegExp.$1)) ? [found] : []) :
                    (element.nodeType !== 1 && element.nodeType !== 9) ? [] :
                    slice.call(
                        classSelectorRE.test(selector) ? (
                            element.getElementsByClassName ? element.getElementsByClassName(RegExp.$1) : qsc(element, RegExp.$1)) :
                        tagSelectorRE.test(selector) ? element.getElementsByTagName(selector) :
                        element.querySelectorAll(selector)
                    )
            } catch (e) {
                return []
            }
        }

        var Z = function(me, dom, selector) {
            dom = dom || []
            me.selector = selector || ''
            me.length = dom.length
            for (var i = 0, j = dom.length; i < j; i++) {
                me[i] = dom[i];
            }
            return me
        }

        var isZ = function(object) {
            return object instanceof Z
        }

        var qsc = function(parent, id) {
            if (parent.getElementsByTagName) {
                var el = parent.getElementsByTagName('*');
                var pattern = new RegExp("(^|\\s)" + id + "(\\s|$)");
                for (var i = 0, j = el.length; i < j; i++) {
                    if (pattern.test(el[i].className)) {
                        return [el[i]];
                    }
                }
            }
            return [];
        }

        vjs.fn = {
            init: function(selector, context) {
                if (!selector) return Z(this);
                else if (selector.nodeType) return Z(this, [selector])
                else {
                    var dom
                    if (isArray(selector)) dom = compact(selector)
                    else if (context !== undefined) return vjs(context).find(selector)
                    else dom = qsa(document, selector)
                    return Z(this, dom, selector);
                }
            },
            find: function(selector) {
                var result, me = this;
                if (typeof selector == 'object')
                    result = vjs(selector).filter(function() {
                        var node = this
                        return [].some.call(me, function(parent) {
                            return vjs.contains(parent, node)
                        })
                    })
                else if (this.length == 1) result = vjs(qsa(this[0], selector))
                else result = this.map(function() {
                    return qsa(this, selector)
                })
                return result
            },
            each: function(callback) {
                if ([].every) {
                    [].every.call(this, function(el, idx) {
                        return callback.call(el, idx, el) !== false
                    });
                } else {
                    for (var i = 0, len = this.length; i < len; i++) {
                        callback.call(this[i], i, this[i]);
                    }
                }

                return this
            },
            hasClass: function(name) {
                var me = this[0];
                return new RegExp('(\\s|^)' + name + '(\\s|$)').test(me.className);
            },
            addClass: function(name) {
                var classNameArray = (name || '').split(/\s+/);
                return this.each(function() {
                    var currClassName = this.className;
                    for (var i = 0, len = classNameArray.length; i < len; i++) {
                        if (!vjs(this).hasClass(classNameArray[i])) {
                            currClassName += ' ' + classNameArray[i];
                        }
                    }
                    this.className = currClassName;
                });
            },
            removeClass: function(name) {
                var classNameArray = (name || '').split(/\s+/);
                return this.each(function() {
                    var currClassName = this.className;
                    for (var i = 0, len = classNameArray.length; i < len; i++) {
                        var reg = new RegExp('(\\s|^)' + classNameArray[i] + '(\\s|$)');
                        currClassName = currClassName.replace(reg, ' ');
                    }

                    this.className = vjs.trim(currClassName);
                })
            },
            on: function(name, callback, context) {
                return this.each(function(i, element) {
                    var evtDelagate = function(e) {
                        e.target = e.target || e.srcElement;
                        callback.call(context, e)
                    }
                    if (!element['domid']) element['domid'] = String(Math.random()).slice(-4);
                    var guid = name + '_' + element['domid'];
                    callback[guid] = evtDelagate;


                    if (element.addEventListener) {
                        element.addEventListener(name, evtDelagate, false);
                    } else if (element.attachEvent) {
                        element.attachEvent('on' + name, evtDelagate);
                    }

                });
            },
            off: function(name, callback, context) {
                return this.each(function(i, element) {
                    var guid = name + '_' + element['domid'],
                        fn = callback[guid] || callback;

                    if (element.removeEventListener) {
                        element.removeEventListener(name, fn, false);
                    } else if (element.detachEvent) {
                        element.detachEvent('on' + name, fn);
                    }
                });
            },
            getStyle: function(styleName) {
                var node = this[0];
                if (browser.msie) {
                    switch (styleName) {
                        // 透明度
                        case "opacity":
                            return ((node.filters['DXImageTransform.Microsoft.Alpha'] ||
                                    node.filters['alpha'] || {}).opacity ||
                                100);
                            // 浮动
                        case "float":
                            styleName = "styleFloat";
                    }
                    return node.style[styleName] ||
                        node.currentStyle ? node.currentStyle[styleName] : 0;
                } else {
                    // 浮动
                    if (styleName == "float") {
                        styleName = "cssFloat";
                    }
                    return node.style[styleName] ||
                        (document.defaultView.getComputedStyle(node, "") ? document.defaultView.getComputedStyle(node, "")[styleName] : null) || 0;
                }
            },
            setStyle: function(styleName, styleValue) {
                return this.each(function() {
                    var node = this;
                    if (browser.msie) {
                        switch (styleName) {
                            case "opacity":
                                node.style.filter = "alpha(opacity=" + (styleValue * 100) + ")";
                                if (!node.currentStyle || !node.currentStyle.hasLayout) {
                                    node.style.zoom = 1;
                                }
                                return;
                            case "float":
                                styleName = "styleFloat";
                        }
                    } else {
                        if (styleName == "float") {
                            styleName = "cssFloat";
                        }
                    }

                    node.style[styleName] = styleValue;
                });
            },
            getAttr: function(name) {
                var node = this[0];
                return node.getAttribute(name);
            },
            setAttr: function(name, value) {
                return this.each(function() {
                    var node = this;
                    node.setAttribute(name, value);
                });
            },
            offset: function() {
                var me = this[0];
                var body = document.body,
                    box = me.getBoundingClientRect();

                return {
                    top: box.top + (window.scrollY || body.parentNode.scrollTop || me.scrollTop) - (document.documentElement.clientTop || body.clientTop || 0),
                    left: box.left + (window.scrollX || body.parentNode.scrollLeft || me.scrollLeft) - (document.documentElement.clientLeft || body.clientLeft || 0)
                };
            },
            width: function(num) {
                if (typeof num == 'undefined') {
                    return this[0].offsetWidth;
                }
                this[0].style.width = parseFloat(num) + 'px';
            },
            height: function(num) {
                if (typeof num == 'undefined') {
                    return this[0].offsetHeight;
                }
                this[0].style.height = parseFloat(num) + 'px';
            },
            map: function(fn) {
                return vjs(vjs.map(this, function(el, i) {
                    return fn.call(el, i, el)
                }))
            }
        }

        vjs.fn.init.prototype = vjs.fn;


        function type(obj) {
            return obj == null ? String(obj) :
                class2type[toString.call(obj)] || "object"
        }

        function isFunction(value) {
            return type(value) == "function"
        }

        function isDocument(obj) {
            return obj != null && (obj.nodeType == 9 || obj.nodeType == obj.DOCUMENT_NODE)
        }

        function isArray(value) {
            return value instanceof Array
        }

        function likeArray(obj) {
            return typeof obj.length == 'number'
        }

        function compact(array) {
            return filter.call(array, function(item) {
                return item != null
            })
        }

        function className(node, value) {
            var klass = node.className,
                svg = klass && klass.baseVal !== undefined

            if (value === undefined) return svg ? klass.baseVal : klass
            svg ? (klass.baseVal = value) : (node.className = value)
        }

        function funcArg(context, arg, idx, payload) {
            return isFunction(arg) ? arg.call(context, idx, payload) : arg
        }


        vjs.contains = function(parent, node) {
            return parent !== node && parent.contains(node)
        }

        vjs.map = function(elements, callback) {
            var value, values = [],
                i, key
            if (likeArray(elements))
                for (i = 0; i < elements.length; i++) {
                    value = callback(elements[i], i)
                    if (value != null) values.push(value)
                } else
                    for (key in elements) {
                        value = callback(elements[key], key)
                        if (value != null) values.push(value)
                    }
            return values
        }

        vjs.each = function(elements, callback) {
            var i, key
            if (likeArray(elements)) {
                for (i = 0; i < elements.length; i++)
                    if (callback.call(this, i, elements[i]) === false) return elements
            } else {
                for (key in elements)
                    if (callback.call(this, key, elements[key]) === false) return elements
            }

            return elements
        }

        vjs.trim = function(str) {
            return str.replace(/^\s\s*/, '').replace(/\s\s*$/, '');
        }

        vjs.each("Boolean Number String Function Array Date RegExp Object".split(" "), function(i, name) {
            class2type["[object " + name + "]"] = name.toLowerCase()
        });

        vjs.extend = function(props) {
            var init, subObj;

            props = props || {};

            init = props['init'] || props.init || this.prototype['init'] || this.prototype.init || function() {};

            subObj = function() {
                init.apply(this, arguments);
            };

            subObj.prototype = vjs.create(this.prototype);
            subObj.prototype.constructor = subObj;

            if (!props.__proto__) props.__proto__ = subObj.prototype;

            subObj.extend = vjs.extend;

            for (var name in props) {
                if (props.hasOwnProperty(name)) {
                    subObj.prototype[name] = props[name];
                }
            }

            return subObj;
        }

        vjs.create = function(obj) {
            function F() {}
            F.prototype = obj;
            return new F();
        };

        vjs.getWinWH = function() {
            var pagerWidth = window.innerWidth,
                pagerHeight = window.innerHeight;

            if (typeof pagerWidth != 'number') {
                if (document.compatMode == 'CSS1Compat') {
                    pagerWidth = document.documentElement.clientWidth;
                    pagerHeight = document.documentElement.clientHeight;
                } else {
                    pagerWidth = document.body.clientWidth;
                    pagerHeight = document.body.clientHeight;
                }
            }
            return {
                width: pagerWidth,
                height: pagerHeight
            }
        }

        vjs.safari = browser.safari;

        return vjs;
    })();
        var emptyFn = function(){};
    var lib = {
        createElement: function(tagName, attributes) {
            var el = document.createElement(tagName),
                attrname;
            for (attrname in attributes) {
                if (attributes.hasOwnProperty(attrname)) {
                    if (attrname.indexOf("-") !== -1) {
                        el.setAttribute(attrname, attributes[attrname]);
                    } else {
                        el[attrname] = attributes[attrname];
                    }
                }
            }
            return el;
        },
        removeElem: function(node) {
            if (node) {
                if (node.remove) {
                    return node.remove();
                } else {
                    return node.parentNode && node.parentNode.removeChild && node.parentNode.removeChild(node);
                }
            }
        },
        el: function(p, n) {
            var elem = n ? $js(p).find(n)[0] : $js(p)[0];
            if (!elem) {
                elem = {
                    "setAttribute": function() {},
                    "style": {},
                    "isnull": true
                };
            }

            return elem;
        },
        //判断是否存在这个元素
        existEl: function(el) {
            if (typeof el === 'object') {
                if (el.isnull) {
                    return false;
                } else if (el instanceof Array) {
                    return el.length > 0;
                } else {
                    return true;
                }
            } else if (typeof el === 'string') {
                return arguments.callee(this.el(el));
            }
            return false;
        },
        now: Date.now || function() {
            return +new Date();
        },
        merge: function(obj1, obj2, safe) {
            if (!obj2) {
                obj2 = {};
            };

            for (var attrname in obj2) {
                if (obj2.hasOwnProperty(attrname) && (!safe || !obj1.hasOwnProperty(attrname))) {
                    obj1[attrname] = obj2[attrname];
                }
            }
            return obj1;
        },
        wsLog: function(data) {},
        debug: function(msg, prefix, line) {
            line = line || " ";

            if (H5AD.config.DEBUG == true || adTools.getQuery("arkdebug")) {
                if (typeof msg == 'object') {
                    if (prefix) {
                        console.log("%c" + prefix, "color:#f0d");
                        this.wsLog(prefix);
                    }
                    this.wsLog(msg);
                    console.log(msg);
                } else {
                    if (msg == undefined) {
                        console.log("数据空" + line)
                        return;
                    }
                    this.wsLog(msg);
                    console.log(msg + line);
                }
            }
        },
        json: function(data) {
            try {
                if (typeof data === "string") {
                    if (JSON && JSON.parse) {
                        return JSON.parse(data);
                    }
                    return eval("(" + data + ")");
                }
                //谨慎使用
                return JSON.stringify(data);
            } catch (ex) {
                return 'error';
            }
        },
         // 对象浅复制
        easyClone: function(raw, target) {
            for (var prop in target) {
                if (target.hasOwnProperty(prop) && typeof target[prop] !== 'object') {
                    raw[prop] = target[prop];
                }
            }
        },
        getJSON: function(param) {
            var url = param.url,
                data = param.data,
                success = param.success,
                fail = param.fail,
                callback = param.callback || 'callback',
                timeout = param.timeout || 5000,
                maxCount = param.maxCount || 2;

            var jsonpCallback,
                count = -1,
                delayID = 0,
                s,
                self = this,
                head = document.head || document.getElementsByTagName('head')[0] || document.documentElement;

            var tmp = [];

            if(data) for(var k in data) tmp.push(k + '=' + data[k]);

            if(!/\?/.test(url)){
                url += '?' + tmp.join('&');
            }else{
                url += '&' + tmp.join('&');
            }

            var addCb = function(){
                var time = self.now(),
                    jsonpCallback = 'vjs_' + time + Math.floor(Math.random()*100);

                window[jsonpCallback] = function(response) {
                    destroy();

                    success.call(this, response,{responseTime: self.now()-time, retryCount: count});

                    window[jsonpCallback] = null;
                };

                return jsonpCallback;
            };

            var destroy = function(){
                if(window[jsonpCallback])  window[jsonpCallback] = emptyFn;
                clearTimeout(delayID);

                if (s && s.parentNode) {
                    head.removeChild(s);

                    s.onload = s.onreadystatechange = null;

                    s = undefined;
                }
            };

            var load = function() {
                destroy();
                count++;
                if (count >= maxCount){
                    fail && fail.call(this);
                    return;
                }

                jsonpCallback = addCb();

                var jsonpUrl = url;

                if(/(\=)\?(&|$)/i.test(jsonpUrl)){
                    jsonpUrl = jsonpUrl.replace(/(\=)\?(&|$)/i,'$1' + jsonpCallback + '$2');
                }else{
                    jsonpUrl += '&' + callback + '=' + jsonpCallback+'&j='+jsonpCallback;
                }

                if(param.log) param.log.pushLog('lib getJSON===' + jsonpUrl + '===' + jsonpCallback + '====' + count);
                s = document.createElement('script');
                s.setAttribute('type', 'text/javascript');
                s.setAttribute('src', jsonpUrl);

                head.insertBefore(s, head.firstChild);

                delayID = setTimeout(load, timeout);
            };

            load();

            return {
                destroy : destroy
            }
        }
    };
    /**
    //以下对lib的使用
    var url = "http://localhost:3000/reso";
    lib.getJSON({url:url,success:function(data){
      alert("nihao");
    }});
    //lib  createElement的使用
    var src = "http://i3.letvimg.com/lc06_iscms/201611/09/23/49/7c2767be74d145a4b9e6eb8f648e46a0.jpg";
    var img = lib.createElement('img', {
          src: src
    });
    $js(img).on('load', function() {
        img = null;
    });
    */
    //
    lib.existEl("box");//这个函数