json数组排序

/*对象*/
function JsonSort(obj, field, sortby) {
this.obj = obj;
this.field = field;
this.sortby = sortby;
}

JsonSort.prototype.sort= function() {
var $this=this;
var ascend = function(a, b) {
return a[$this.field] > b[$this.field] ? 1 : -1;
};
var descend = function(a, b) {
return a[$this.field] > b[$this.field] ? -1 : 1;
};
if (this.sortby == "ascend") {
this.obj.sort(ascend);
} else {
this.obj.sort(descend);
}
};
var json = [{
name: 'kavan',
age: 25
}, {
name: 'elle',
age: 24
}, {
name: 'jek',
age: 22
}];

var jsonSort=new JsonSort(json,'age','ascend');
jsonSort.sort();
console.log(json);