JS遍历二维数组

 //求平均数
 var pjs=[
         ['小明',87],
         ['小红',81],
         ['小花',97],
         ['小天',76],
         ['小张',74],
         ['小小',94],
         ['小西',90],
         ['小武',76],
         ['小迪',64],
         ['小曼',76]
 ]
 var i,j;
 var sum=0;
 for(var i=0;i<pjs.length;i++){
 
   for(j=0;j<pjs[i].length;j++)
   {
       if(j==pjs[i].length-1)
       {
           sum+=pjs[i][j];
           
       }
       
   }
 }
 sum=sum/pjs.length
 document.write(sum+"<br />");