数组功能函数

将一维数组转换为二维数组

es5
Array.prototype.erwei=function(){

if(!(this instanceof Array))new TypeError("parameter is wrong");

if(this.length==0){ var a=[],b;a[a.length]=this; b=a;return b }

return this.map(function(current,index,array){
    return [current];
})

}