一个关于传参数js数组的封装方法(寄生模式)

function createArr(){
var arr = new Array();
arr.push.apply(arr,arguments);

arr.toJoin = function(){
return this.join(",");
}
arr.toSlice = function(start,end){//start num  //end num
return Array.prototype.slice.call(this,start,end+1)
}

return arr;
}

var c = new createArr("a","b","c","d");

c.toSlice(1,4)
//["b", "c", "d"]