javascript 如何定义一个多维数组

var caidan_pic = new Array();for(var i=1 ; i<=caidan_arr.length ; i++) { caidan_pic[i] = new Array(); for(var j=0 ; j<caidan_arr[i].length ; j++) { alert(j); caidan_pic[i][j] = "imgs/"+i+"_"+j+".png"; alert(caidan_pic[i][j]); }}