这个啰嗦的啊...

obj.sort( function(curr,next) {
    return !!( curr.age-next.age )? curr.age-next.age: curr.top-next.top;
} );

这不就好了吗

用自带的就是了

    obj = obj.sort((a, b) =>  { return a.age - b.age || b.top - a.top;} );
    console.log(obj);
    
    

因为你说的是 top从高到低排序 这种写法是数字越大越在前面
你要是想要越小的话
你修改一下位置就好了 b.top - a.top 改成 a.top - b.top

在线体验 https://jsfiddle.net/hguyjgs8/1/

//假设top 不大于1000, 大于1000的，适度修改
var obj = [{
  id: 1,
  age: 20,
  top: 5
}, {
  id: 3,
  age: 21,
  top: 6
}, {
  id: 2,
  age: 20,
  top: 8
}]

function pad(num, size) {
  var s = num + "";
  while (s.length < size) s = "0" + s;
  return s;
}

obj.sort((a, b) => pad(a.age, 2) + pad(1000-a.top, 3) > pad(b.age, 2)  + pad(1000-b.top, 3)).forEach((i) => {
    document.writeln(JSON.stringify(i)+'<br>');
});

function keySort (...args) {
    let props = args.map(name => {
        let desc = name[0] === '-'
        if (desc) name = name.substring(1)
        return { desc, name }
    })
    
    return (a, b) => {
        let result = 0
        for (let prop of props) {
            let p = prop.name
            result = prop.desc ? b[p] - a[p] : a[p] - b[p]
            if (result) return result
        }
        return result
    }
}

obj.sort(keySort('age', '-top'))

https://jsfiddle.net/sojxjqpf/

Who First

var whoFirst = ['age', 'top']; 

var copy = o => JSON.parse(
    JSON.stringify(o)
); 

var judge = (a, b, whos) => {
    if (whos.length === 0) return 0; 
    
    let key = whos[0]; 
    if (a[key] !== b[key]){
        return a[key] - b[key]; 
    } else {
        return judge(a, b, whos.slice(1)); 
    }
}

Next

var sorts = arr => {
    let a = copy(arr); 

    a.sort((a, b) => {
        return judge(a, b, whoFirst); 
    }); 
    
    return a; 
}

S

WhoFirst 升序。

var obj = [{
    id : 1,
    age : 20,
        top :5
},{
    id : 3,
    age : 21,
        top : 6
},{
    id : 2,
    age : 20,
        top : 8
},{
    id: 4,
    age: 20, 
    top: 2
},{
    id: 8,
    age: 20, 
    top: 2
},{
    id: 5,
    age: 20, 
    top: 11
},{
    id: 7,
    age: 20, 
    top: 9
},{
    id: 6,
    age: 20, 
    top: 2
},{
    id: 9,
    age: 20, 
    top: 1
}]; 


sorts(obj);