从JavaScript中的Object.entries中的数组破坏 [英] Array destructing from Object.entries in Javascript

问题描述

这里是代码：

  const posts = [{数据：{id：1，date：2019-02-03，ev_filter_1：[art，foodie]，ev_filter_2：[value1，value2]，ev_filter_3：[value1，value2 ]，ev_filter_4：[all，12+]}}，{data：{id：2，date：，ev_filter_1：[arti，foodie]，ev_filter_2：[value1 value2]，ev_filter_3：[value1，value2]，ev_filter_4：[all，19+]}}，{data：{id：3，date：2019-02-03 ev_filter_1：[art，food，ev_filter_2：[value1，value75]，ev_filter_3：[value1，value2]，ev_filter_4：[all，12+]}} ];函数sift2（arrObjLit，pattern，... values）{const toMatch = new Set（values）const result = arrObjLit.map（o => o.data）.filter（o => Object.entries（o）.filter（（[k，v]）=> {console.log（`$ {k}：$ {v}`）return true}）.filter（（[k，v]）=> k.startsWith（pattern））.filter（（[k，v] ）=> Array.isArray（v））.filter（（[k，v]）=> toMatch.has（v））.length> 0）return result;} console.log（... sift2（posts，ev_，value75，12 +））;  

这让我感到困惑基于此帖
我期望在过滤器中的数组破坏是错误的。但是，不是。这正是我正在寻找的。为什么破解在过滤器方法中是平的？我观察到错误吗？

  .filter（o => 
 Object.entries（o）
 .filter（（[k，v]）=> k.startsWith（pattern））
  

条目的输出上调用第二个过滤器 code>。请注意，您正在使用

  .filter（o => Object.entries（o）.filter （...）... 
  

而不是

  .map（Object.entries）.filter（o => o。...）
  

---

表示，我会将您的功能重写为

  function sift2（arrObjLit，pattern，... values）{
 const toMatch = new Set（values）
 return arrObjLit.filter（o => 
 Object.entries .data）
 .some（（[k，v]）=> {
 console.log（`$ {k}：$ {v}`）; 
 return k.startsWith （图案）
&&& Array.isArray（v）
&& v.some（x => toMatch.has（x））; 
}）
）; 
} 
  

Here is the code in question:

const posts = [{
  data: {
    id: 1,
    date: "2019-02-03",
    ev_filter_1: ["art", "foodie"],
    ev_filter_2: ["value1", "value2"],
    ev_filter_3: ["value1", "value2"],
    ev_filter_4: ["all", "12+"]
  }
},
  {
    data: {
      id: 2,
      date: "",
      ev_filter_1: ["arti", "foodie"],
      ev_filter_2: ["value1", "value2"],
      ev_filter_3: ["value1", "value2"],
      ev_filter_4: ["all", "19+"]
    }
  },
  {
    data: {
      id: 3,
      date: "2019-02-03",
      ev_filter_1: ["art", "foodie"],
      ev_filter_2: ["value1", "value75"],
      ev_filter_3: ["value1", "value2"],
      ev_filter_4: ["all", "12+"]
    }
  }
];

function sift2(arrObjLit, pattern, ...values) {
  const toMatch = new Set(values)
  const result = arrObjLit.map(o => o.data)
  .filter(o =>
      Object.entries(o)
      .filter(([k, v]) => {
        console.log(`${k}: ${v}`)
        return true
      })
      .filter(([k, v]) => k.startsWith(pattern))
      .filter(([k, v]) => Array.isArray(v))
      .filter(([k, v]) => toMatch.has(v))
          .length > 0
  )
  return result;
}

console.log(...sift2(posts, "ev_", "value75", "12+"));

Which is baffling me. Based on this post I would expect the array destructing in filter to be wrong. And yet, it's not. It's exactly what I am looking for. Why would the destructing be flat in the filter method? Am I observing things wrong?

.filter(o =>
      Object.entries(o)
      .filter(([k, v]) => k.startsWith(pattern))

解决方案

Because you are now properly nesting the iterations, calling the second filter directly on the output of entries. Notice that you are using

.filter(o => Object.entries(o).filter(…).… )

instead of

.map(Object.entries).filter(o => o.… )

---

That said, I'd rewrite your function to

function sift2(arrObjLit, pattern, ...values) {
  const toMatch = new Set(values)
  return arrObjLit.filter(o =>
    Object.entries(o.data)
    .some(([k, v]) => {
      console.log(`${k}: ${v}`);
      return k.startsWith(pattern)
          && Array.isArray(v)
          && v.some(x => toMatch.has(x));
    })
  );
}

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