纯文字的json字符串，怎么分割成几个字一组，并追加进去

self.contents = [{"pageCount":0,"author":"(清)任在陞，(清)李柱明纂修 ","catalogData":"封面=1=1;序=2=1;目录=29=1;图=33=1;卷之一=47=1;卷之二=103=1;图=183=1;","title":"[康熙]平谷县志","bookname":"康熙平谷县志","description":"","pages":[],"bookInfo":"ZhongYi馬□馴□史張御史永樂賈忠知縣史縉經歴李序班劉賢兵馬呉羿序班王鋼縣丞唐敔知縣秦定序班張璡序班潘厚大使楊知縣馬良廵檢賈輔署正米黍知縣蕭瑍司獄賈智主事路澄知縣張譲馬庚御史遜逹知縣張敬治中","publisher":""}]
        var disName =self.contents[0].bookInfo;
        console.log("92--"+disName);
        var str=Math.ceil(disName.length/20)
        for(var i=0;i<str;i++){
            console.log("94---"+disName.substring(i*20,(i+1)*20));
            //self.contents[0].bookInfo = disName.substring(i*20,(i+1)*20);
            var span = ""
        }