var HtmlUtil = {
        /*1.用浏览器内部转换器实现html编码（转义）*/
        htmlEncode:function (html){
            //1.首先动态创建一个容器标签元素，如DIV
            var temp = document.createElement ("div");
            //2.然后将要转换的字符串设置为这个元素的innerText或者textContent
            (temp.textContent != undefined ) ? (temp.textContent = html) : (temp.innerText = html);
            //3.最后返回这个元素的innerHTML，即得到经过HTML编码转换的字符串了
            var output = temp.innerHTML;
            temp = null;
            return output;
        },
        /*2.用浏览器内部转换器实现html解码（反转义）*/
        htmlDecode:function (text){
            //1.首先动态创建一个容器标签元素，如DIV
            var temp = document.createElement("div");
            //2.然后将要转换的字符串设置为这个元素的innerHTML(ie，火狐，google都支持)
            temp.innerHTML = text;
            //3.最后返回这个元素的innerText或者textContent，即得到经过HTML解码的字符串了。
            var output = temp.innerText || temp.textContent;
            temp = null;
            return output;
        },
        /*3.用正则表达式实现html编码（转义）*/
        htmlEncodeByRegExp:function (str){
             var temp = "";
             if(str.length == 0) return "";
             temp = str.replace(/&/g,"&");
             temp = temp.replace(/</g,"<");
             temp = temp.replace(/>/g,">");
             temp = temp.replace(/\s/g," ");
             temp = temp.replace(/\'/g,"'");
             temp = temp.replace(/\"/g,""");
             return temp;
        },
        /*4.用正则表达式实现html解码（反转义）*/
        htmlDecodeByRegExp:function (str){
             var temp = "";
             if(str.length == 0) return "";
             temp = str.replace(/&/g,"&");
             temp = temp.replace(/</g,"<");
             temp = temp.replace(/>/g,">");
             temp = temp.replace(/ /g," ");
             temp = temp.replace(/'/g,"\'");
             temp = temp.replace(/"/g,"\"");
             return temp;
        },
        /*5.用正则表达式实现html编码（转义）（另一种写法）*/
        html2Escape:function(sHtml) {
             return sHtml.replace(/[<>&"]/g,function(c){return {'<':'<','>':'>','&':'&','"':'"'}[c];});
        },
        /*6.用正则表达式实现html解码（反转义）（另一种写法）*/
        escape2Html:function (str) {
             var arrEntities={'lt':'<','gt':'>','nbsp':' ','amp':'&','quot':'"'};
             return str.replace(/&(lt|gt|nbsp|amp|quot);/ig,function(all,t){return arrEntities[t];});
        }
    };

参考：

https://www.cnblogs.com/willingtolove/p/11059325.html