如何使用javascript仅迭代嵌套对象的顶级键？

Question

For example, if I were to iterate through the following object:

{
  "Crows": {
    "players": {
      "Ben": {
        "jersey #": "1B"
      },
      "Ty": {
        "jersey #": "2B"
      }
    }
  },
  "Pigeons": {
    "players": {
      "Bill": {
        "jersey #": "1B"
      },
      "Tim": {
        "jersey #": "2B"
      }
    }
  },
  "Seagulls": {
    "players": {
      "Bob": {
        "jersey #": "1B"
      },
      "Tom": {
        "jersey #": "2B"
      }
    }
  }
}

I want to only iterate and manipulate the top level keys, which in this case are "Crows", "Pigeons", and "Seagulls".

When I try to iterate with a traditional for (var key in data) loop, a console.log of the keys gives me every key in the object, including the nested ones like "players". How would I only loop through parent keys?

Answer 1

First, JSON is a string format for transporting data over HTTP/HTTPS. You don't iterate JSON, you parse it back into a regular JavaScript object and then you do whatever you like with that object. What you've posted is just a plain JavaScript object, so it looks like you've already done that parsing.

So, in your case:

 let result = { "Crows": { "players": { "Ben": { "jersey #": "1B" }, "Ty": { "jersey #": "2B" } } }, "Pigeons": { "players": { "Bill": { "jersey #": "1B" }, "Tim": { "jersey #": "2B" } } }, "Seagulls": { "players": { "Bob": { "jersey #": "1B" }, "Tom": { "jersey #": "2B" } } } }; for(var prop in result){ console.log(prop); // Just get the property name only console.log(result[prop]); // Or, get the data held in that property // Or, dig deeper still. Either of the following syntaxes will work: console.log(result[prop]["players"]); console.log(result[prop].players); }

Answer 2

Either use a for...in loop:

 const data = { "Crows": { "players": { "Ben": { "jersey #": "1B" }, "Ty": { "jersey #": "2B" } } }, "Pigeons": { "players": { "Bill": { "jersey #": "1B" }, "Tim": { "jersey #": "2B" } } }, "Seagulls": { "players": { "Bob": { "jersey #": "1B" }, "Tom": { "jersey #": "2B" } } } } for (let key in data) { console.log(key); }

Or collect them into one array:

 const data = { "Crows": { "players": { "Ben": { "jersey #": "1B" }, "Ty": { "jersey #": "2B" } } }, "Pigeons": { "players": { "Bill": { "jersey #": "1B" }, "Tim": { "jersey #": "2B" } } }, "Seagulls": { "players": { "Bob": { "jersey #": "1B" }, "Tom": { "jersey #": "2B" } } } } console.log(Object.keys(data));