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 />");