JavaScript 根据另一个对象数组的属性过滤对象数组

Question

我有 2 个对象数组

Tasks
[{
 name: "test",
 type: "one"
},
{
 name: "test2",
 type: 'two'
}]

事件

[{
 name: "test",
 type: "one"
},
{
 name: "test2",
 type: 'two'
},
{
 name: "test3",
 type: "three"
 }]

如何根据任务数组的属性过滤事件数组？我想要这个结果。

事件

[{
 name: "test",
 type: "one"
},
{
 name: "test2",
 type: 'two'
}]

我试过使用 .filter()，但它返回一个空集合。

let tests = activities.filter(x => tasks.includes(x.type));

如何在 Javascript 中实现这一点？

Answer 1

filter 是正确的工具，但 includes 不是。 tasks 中的条目是对象，而不是字符串；它们都不匹配 tests 中的任何类型。

相反，简单版本使用 some查看 tasks 中的任何条目是否与正在测试的事件类型相匹配:

let tests = activities.filter(a => tasks.some(t => t.type == a.type));

实例:

const tasks = [
  {
    name: "test",
    type: "one"
  },
  {
    name: "test2",
    type: 'two'
  }
];
const activities = [
  {
    name: "test",
    type: "one"
  },
  {
    name: "test2",
    type: 'two'
  },
  {
    name: "test3",
    type: "three"
  }
];
 
let tests = activities.filter(a => tasks.some(t => t.type == a.type));
console.log(tests);

.as-console-wrapper {
  max-height: 100% !important;
}

自然地，这意味着至少要为 activities 中的每个条目部分地重新遍历 tasks。对于您展示的示例，这绝对没问题；如果 tasks 有数十万个条目，或者这是在一个紧密的循环中完成的，则不会太多。 :-)

在这种情况下，您可以预先从tasks 中给自己一组已知类型，然后仅针对该集合进行测试:

const knownTypes = new Set();
for (const task of tasks) {
    knownTypes.add(task.type);
}
let tests = activities.filter(a => knownTypes.has(a.type));

实例:

const tasks = [
  {
    name: "test",
    type: "one"
  },
  {
    name: "test2",
    type: 'two'
  }
];
const activities = [
  {
    name: "test",
    type: "one"
  },
  {
    name: "test2",
    type: 'two'
  },
  {
    name: "test3",
    type: "three"
  }
];
 
const knownTypes = new Set();
for (const task of tasks) {
    knownTypes.add(task.type);
}
let tests = activities.filter(a => knownTypes.has(a.type));
console.log(tests);

.as-console-wrapper {
  max-height: 100% !important;
}

或者，除了 Set，您还可以为 knownTypes 使用对象，通过 Object.create(null) 创建它- 有可能你的任何类型恰好与 Object.prototype 上的属性同名:

const knownTypes = Object.create(null);
for (const task of tasks) {
    knownTypes[task.type] = true;
}
let tests = activities.filter(a => knownTypes[a.type]);

实例:

const tasks = [
  {
    name: "test",
    type: "one"
  },
  {
    name: "test2",
    type: 'two'
  }
];
const activities = [
  {
    name: "test",
    type: "one"
  },
  {
    name: "test2",
    type: 'two'
  },
  {
    name: "test3",
    type: "three"
  }
];
 
const knownTypes = Object.create(null);
for (const task of tasks) {
    knownTypes[task.type] = true;
}
let tests = activities.filter(a => knownTypes[a.type]);
console.log(tests);

.as-console-wrapper {
  max-height: 100% !important;
}