SOURCE

function at(object, arr) {
  //
  var value = "";
  for(let i  = 0; i < arr.length; i++) {
     var key = arr[i];
     value +=  eval("object."+key);
    if(!i)value += ",";
  }
  return value;
}

const object = {
  'a': [  {
       'b':
        { 'c': 3, },
         }, 
         4, ],
          };

// 输出 [3, 4]
console.log(at(object, ['a[0].b.c', 'a[1]']));