我使用内置在JavaScript Object中的Object.keys，它将返回来自给定对象MDN Reference的键数组

const person = {
  name: "Jeeva",
  age: "22",
  gender: "Male"
}
console.log(Object.keys(person))

试试这个

var s = {name: "raul", age: "22", gender: "Male"}
   var keys = [];
   for(var k in s) keys.push(k);

这里keys数组将返回你的keys ["name", "age", "gender"]

var input = {"document":
  {"people":[
    {"name":["Harry Potter"],"age":["18"],"gender":["Male"]},
    {"name":["hermione granger"],"age":["18"],"gender":["Female"]},
  ]}
}

var keys = [];
for(var i = 0;i<input.document.people.length;i++)
{
    Object.keys(input.document.people[i]).forEach(function(key){
        if(keys.indexOf(key) == -1)
        {
            keys.push(key);
        }
    });
}
console.log(keys);

今天的ES6

const json_getAllKeys = data => (
  data.reduce((keys, obj) => (
    keys.concat(Object.keys(obj).filter(key => (
      keys.indexOf(key) === -1))
    )
  ), [])
)

是的，它可以写在很长的一行;

const json_getAllKeys = data => data.reduce((keys, obj) => keys.concat(Object.keys(obj).filter(key => keys.indexOf(key) === -1)), [])

EDIT：如果输入是对象数组类型，则返回所有一阶键

这个函数应该返回一个包含ALL键的数组（即JSON对象中的键名称），包括嵌套的键/值对。

function get_all_json_keys(json_object, ret_array = []) {
    for (json_key in json_object) {
        if (typeof(json_object[json_key]) === 'object' && !Array.isArray(json_object[json_key])) {
            ret_array.push(json_key);
            get_all_json_keys(json_object[json_key], ret_array);
        } else if (Array.isArray(json_object[json_key])) {
            ret_array.push(json_key);
            first_element = json_object[json_key][0];
            if (typeof(first_element) === 'object') {
                get_all_json_keys(first_element, ret_array);
            }
        } else {
            ret_array.push(json_key);
        }
    }

    return ret_array
}

在OP的原始对象上使用此函数

const op_object =
{
    "document":{
       "people":[
          {
             "name":[
                "Harry Potter"
             ],
             "age":[
                "18"
             ],
             "gender":[
                "Male"
             ]
          },
          {
             "name":[
                "hermione granger"
             ],
             "age":[
                "18"
             ],
             "gender":[
                "Female"
             ]
          }
       ]
    }
 }

var all_keys = [];

function get_all_json_keys(json_object, ret_array = []) {
    for (json_key in json_object) {
        if (typeof(json_object[json_key]) === 'object' && !Array.isArray(json_object[json_key])) {
            ret_array.push(json_key);
            get_all_json_keys(json_object[json_key], ret_array);
        } else if (Array.isArray(json_object[json_key])) {
            ret_array.push(json_key);
            first_element = json_object[json_key][0];
            if (typeof(first_element) === 'object') {
                get_all_json_keys(first_element, ret_array);
            }
        } else {
            ret_array.push(json_key);
        }
    }

    return ret_array
}

get_all_json_keys(op_object, all_keys);

console.log(all_keys);

应产生
[ 'document', 'people', 'name', 'age', 'gender' ]
注意：这将返回一个唯一的所有键名称列表。

var jsonData = { Name: "Ricardo Vasquez", age: "46", Email: "[email protected]" };

for (x in jsonData) {   
  console.log(x +" => "+ jsonData[x]);  
  alert(x +" => "+  jsonData[x]);  
  }

我们必须“解析”jsonObject

console.log('{"key0":"value0", "key1":"value1"}'); 
    var jsonObject = JSON.parse('{"key0":"value0", "key1":"value1"}')
    Object.keys(jsonObject).forEach(key => { 
        console.log(jsonObject[key]); //values 
        console.log(key); //keys 
    })