man是自定义的对象，使用var tim = JSON.stringify(man); var newman=JSON.parse(tim)后newman的类型是“object”并不是一个Man，怎么才能变回一个Man呢？

function Man() {
    this._type = "man";
    this.name="";
    this.run = function () {
        alert("run!!");
        alert(this.name);
    }
}
var st = new Man();
st.name="tom";
var tt = JSON.stringify(st);
var sb=JSON.parse(tt)
console.log(sb);
var m1 = JSON.parse(tt,function(key,val){
    if(typeof(val) === 'object'&&val._type === 'man'){
        var m=new Man();
        console.log(val);
        console.log(val.name);
        m.name=val.name;
        return m;
    }
    return val;
});
console.log(m1);
m1.run();