Question

我想获取对象数组中的所有键。最初我只是抓住了数组中的第一个对象并使用了：

var keys = Object.keys(tableData[0]);

但是当我仔细观察数据时，我注意到第一行没有包含所有需要的键。在下面的示例中，第三个项目包含所有键，但您可能遇到了获取所有键需要组合多个对象的情况。

var tableData = [
  { first:"jeff", last:"doe", phone: "2891" },
  { first:"sarah", phone:"this", county: "usa" }
  { first:"bob", last:"brown", county: "usa", phone: "23211" }
];

如何获得大规模高效的对象数组中的所有唯一键？

Answer 1

您可以使用reduce()和Set来获得所需的结果。

var array = [
  { first:"jeff", last:"doe", phone: "2891" },
  { first:"sarah", phone:"this", county: "usa" },
  { first:"bob", last:"brown", county: "usa", phone: "23211" }
];

var keys = [...new Set(array.reduce(function(r, e) {
  r = r.concat(Object.keys(e));
  return r;
}, []))];

console.log(keys)

Answer 2

您可以按照以下步骤进行操作;

var array = [ { first:"jeff", last:"doe", phone: "2891" }, { first:"sarah", phone:"this", county: "usa" }, { first:"bob", last:"brown", county: "usa", phone: "23211" } ]; var result = array.reduce((p,o) => Object.assign(p,Object.keys(o)),[]); console.log(result);

根据一个非常合理的评论，这是我的下一个解决方案;

＆＃13;

var array = [
  { first:"jeff", last:"doe", phone: "2891", moron: "me"},
  { first:"sarah", phone:"this", county: "usa" },
  { first:"bob", last:"brown", county: "usa", phone: "23211" }
];

var result = array.reduce((p,o) => p.concat(Object.keys(o).filter(k => !p.includes(k))),[]);
console.log(result);

＆＃13;

Answer 3

您可以使用map()和Set：

＆＃13;

var arr = [
  { first:"jeff", last:"doe", phone: "2891", something: "4" },
  { first:"sarah", phone:"this", county: "usa" },
  { first:"bob", last:"brown", county: "usa", phone: "23211", lastrow: "lr" }
];

var set = new Set();
arr.map(obj => {
  Object.keys(obj).forEach(el => {
    set.add(el);
  });
});
var res = [...set];
console.log(res);

＆＃13;

我已使用@Nenad Vracar和@Redu中的代码测试了上述代码中Chrome浏览器中的console time：

var array = [
    { first:"jeff", last:"doe", phone: "2891", something: "4" },
    { first:"sarah", phone:"this", county: "usa" },
    { first:"bob", last:"brown", county: "usa", phone: "23211", lastrow: "lr" }
];

function f1(arr) { // Peter Leger
    var set = new Set();
    arr.map(obj => {
        Object.keys(obj).forEach(el => {
            set.add(el);
        });
    });
    var res = [...set];
    return res; 
} 

function f2(arr) { // Nenad Vracar
    var keys = [...new Set(arr.reduce(function(r, e) {
        r = r.concat(Object.keys(e));
        return r;
    }, []))];
    return keys;
}

function f3(arr) { // Redu
    var result = arr.reduce((p,o) => p.concat(Object.keys(o).filter(k => !p.includes(k))),[]);
    return result;
}

var iterations = 1000000;
console.time('Function f1');
for(var i = 0; i < iterations; i++ ){
    f1(array);
};
console.timeEnd('Function f1')

console.time('Function f2');
for(var i = 0; i < iterations; i++ ){
    f2(array);
};
console.timeEnd('Function f2')

console.time('Function f3');
for(var i = 0; i < iterations; i++ ){
    f3(array);
};
console.timeEnd('Function f3')

具有以下结果：

第一个结果：

功能f1：6375.193ms
功能f2：6309.516ms
功能f3：6756.946ms

第二个结果：

功能f1：6152.040ms
功能f2：8004.565ms
功能f3：6885.656ms

第三个结果：

功能f1：5918.497ms
功能f2：8136.073ms
功能f3：7111.273ms

在无组织的对象数组中获取所有键的有效方法

3 个答案: