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