js将json格式的'cm'，通过循环或其他方式生成'col'

// js将json格式的'cm'，通过循环或其他方式生成'col'。（不拼接字符串）

 var cm = '[{"1":"S", "2":"M", "3":"L"}, {"1":"23", "2":"24"}, {"1":"28", "2":"29", "3":"30"}, {"1":"B28", "2":"B29", "3":"B30"}]';

var col =   [
            { display: 'S', 
              columns: [{ display: '23', 
                           columns: [{display: '28', 
                                      columns: [{ display: 'B28', name: 'ContactName', width: 100, align: 'left'}]
                                    }]
                        }]
            },

            { display: 'M', 
              columns: [{ display: '24', 
                           columns: [{display: '29', 
                                      columns: [{ display: 'B29', name: 'ContactName', width: 100, align: 'left'}]
                                    }]
                        }]
            },

            { display: 'L', 
              columns: [{ display: '', 
                           columns: [{display: '30', 
                                      columns: [{ display: 'B30', name: 'ContactName', width: 100, align: 'left'}]
                                    }]
                        }]
            }               
            ];

 <body>
<div id='testShow'></div>
<script>
var cm = '[{"1":"S", "2":"M", "3":"L"}, {"1":"23", "2":"24"}, {"1":"28", "2":"29", "3":"30"}, {"1":"B28", "2":"B29", "3":"B30"}]';
var cmJSON = JSON.parse(cm);
var col = new Array(3);
var colObj=new Array(3);
for(var i=0;i<cmJSON.length;i++){
   for(var j=0;j<col.length;j++){
       var value = cmJSON[i][(j+1)+""]?cmJSON[i][(j+1)+""]:"";
       if(!col[j]) {
           col[j]={};
           colObj[j]=col[j];
       }else{
          colObj[j]['columns']=[{}];
          colObj[j]= colObj[j]['columns'][0];
       }
       colObj[j]['display'] = value ;
       if(i==cmJSON.length-1){
         colObj[j]['name']= 'ContactName';
         colObj[j]['width']= 100;
         colObj[j]['align']='left';
       }
   }
}
colObj.length=0;
document.getElementById('testShow').innerHTML=JSON.stringify(col);
</script>
</body>