减少javascript中的对象数组答案

【问题标题】：Reduce array of objects in javascript减少javascript中的对象数组
【发布时间】：2020-01-27 16:46:42
【问题描述】：

我在 javascript 中有一个我想减少的对象数组。请参阅下面的代码。 6 位或更多数字的消息已验证，未验证的消息较少。我按组分组。

const myArray = [
  { group: 'groupA', message: 'Text without a number', sl: '1A' },
  { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupB', message: 'Text without a number', sl: '1A' },
  { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupB', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupC', message: 'Text without a number', sl: '1B' },
  { group: 'groupD', message: 'Text with a number Tick0127866', sl: '1B' },
  { group: 'groupC', message: 'Text without a number', sl: '1A' }
];

output = myArray.reduce((acc, line) => {
  let yes = 0;
  let no = 0;

  line.message.match(/\d{6,}/) ? yes++ : no++;

  acc[line.group] = acc[line.group] || {};
  acc[line.group].verified = (acc[line.group].verified || 0) + yes;
  acc[line.group].unverified = (acc[line.group].unverified || 0) + no;
  return acc;
}, {});

console.log('output', output);

但是我希望输出也是一个对象数组，如下所示：

[
  { group: 'groupA', verified: 2, unverified: 1 },
  { group: 'groupB', verified: 1, unverified: 1 },
  { group: 'groupC', verified: 0, unverified: 2 },
  { group: 'groupD', verified: 1, unverified: 0 }
]

我该怎么做？

【问题讨论】：

更改逻辑并使用数组（myArray.reduce((acc, line) => ..., [])），或者之后使用Object.entries() + .map()转换结果
你能提供一些关于你为什么要达到的背景吗？您将已验证和未验证的属性用于/需要什么？
感谢大家的快速回答！我将使用输出作为 d3.js 堆叠条形图的输入，其中包含月度数据。

标签： javascript arrays object reduce

【解决方案1】：

使用数组作为累加器的初始值，在 .reduce 内部，使用 findIndex 检查当前组，如果找到，更新 verified 和 unverified 值，否则，插入一个新值：

const myArray = [
  { group: "groupA", message: "Text without a number", sl: "1A" },
  { group: "groupA", message: "Text with a number WO5467829", sl: "1A" },
  { group: "groupB", message: "Text without a number", sl: "1A" },
  { group: "groupA", message: "Text with a number WO5467829", sl: "1A" },
  { group: "groupB", message: "Text with a number WO5467829", sl: "1A" },
  { group: "groupC", message: "Text without a number", sl: "1B" },
  { group: "groupD", message: "Text with a number Tick0127866", sl: "1B" },
  { group: "groupC", message: "Text without a number", sl: "1A" }
];

output = myArray.reduce((acc, line) => {
  let yes = 0;
  let no = 0;

  line.message.match(/\d{6,}/) ? yes++ : no++;

  // check if you have the group in the accumulator
  const ndx = acc.findIndex(e => e.group === line.group);

  // if you have it, manipulate verified and unverified
  if (ndx > -1) {
    acc[ndx].verified = (acc[ndx].verified || 0) + yes;
    acc[ndx].unverified = (acc[ndx].unverified || 0) + no;
  } else {
    // insert a new entry instead
    acc.push({
      group: line.group,
      verified: yes,
      unverified: no
    });
  }

  return acc;
}, []); // use an array as the initial value of the accumulator

console.log(output);

【讨论】：

【解决方案2】：

您可以使用Object.entries() 或Object.keys() 简单地扩展您的解决方案/输出以获得实际所需的输出。我将使用Object.entries()

const myArray = [
  { group: 'groupA', message: 'Text without a number', sl: '1A' },
  { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupB', message: 'Text without a number', sl: '1A' },
  { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupB', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupC', message: 'Text without a number', sl: '1B' },
  { group: 'groupD', message: 'Text with a number Tick0127866', sl: '1B' },
  { group: 'groupC', message: 'Text without a number', sl: '1A' }
];

output = myArray.reduce((acc, line) => {
  let yes = 0;
  let no = 0;

  line.message.match(/\d{6,}/) ? yes++ : no++;

  acc[line.group] = acc[line.group] || {};
  acc[line.group].verified = (acc[line.group].verified || 0) + yes;
  acc[line.group].unverified = (acc[line.group].unverified || 0) + no;
  return acc;
}, {});

console.log('output', output);

const actualOutput = Object.entries(output).map(([group, value]) => ({group, ...value }));

console.log(actualOutput);

【讨论】：

【解决方案3】：

我忍不住对您的代码进行了一点重构。那就是说。我做了什么：

使用数组 ([]) 启动累加器
如果尚未初始化，则将组推送到数组中
增加 verified 或 unverified 取决于您的测试是否失败

const myArray = [
  { group: "groupA", message: "Text without a number", sl: "1A" },
  { group: "groupA", message: "Text with a number WO5467829", sl: "1A" },
  { group: "groupB", message: "Text without a number", sl: "1A" },
  { group: "groupA", message: "Text with a number WO5467829", sl: "1A" },
  { group: "groupB", message: "Text with a number WO5467829", sl: "1A" },
  { group: "groupC", message: "Text without a number", sl: "1B" },
  { group: "groupD", message: "Text with a number Tick0127866", sl: "1B" },
  { group: "groupC", message: "Text without a number", sl: "1A" }
];

output = myArray.reduce((acc, line) => {
  if( acc.findIndex(e => e.group === line.group) === -1 ) {
  	acc.push({
      group: line.group,
      verified: 0,
      unverified: 0
    });
  }
  
  let group = acc.find(e => e.group === line.group);

  if( line.message.match(/\d{6,}/) )
  	group.verified++;
  else
  	group.unverified++;

  return acc;
}, []);

console.log(output);

【讨论】：

【解决方案4】：

将groupprop 放入您的帐户中。然后使用Object.values函数返回一个对象的值。

const myArray = [
  { group: 'groupA', message: 'Text without a number', sl: '1A' },
  { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupB', message: 'Text without a number', sl: '1A' },
  { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupB', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupC', message: 'Text without a number', sl: '1B' },
  { group: 'groupD', message: 'Text with a number Tick0127866', sl: '1B' },
  { group: 'groupC', message: 'Text without a number', sl: '1A' }
];

output = myArray.reduce((acc, line) => {
  let yes = 0;
  let no = 0;

  line.message.match(/\d{6,}/) ? yes++ : no++;

  acc[line.group] = acc[line.group] || {};
  acc[line.group].group = line.group;
  acc[line.group].verified = (acc[line.group].verified || 0) + yes;
  acc[line.group].unverified = (acc[line.group].unverified || 0) + no;
  return acc;
}, {});

console.log('output', Object.values(output));

【讨论】：

有人似乎对所有答案都投了反对票。
可能只是对回答没有尝试的问题的惩罚。但我认为 OP 的代码足够接近，这不是“为我编写代码”的问题。
@Barmar 这个尝试就够了。与我通常看到的这类问题相比，我的意思是太多了。
@MaheerAli 没错。 reduce 代码是最难的部分。
谢谢，不是我投反对票，对帮助感到满意

【解决方案5】：

您可以在Object.entries 上使用map()。我还在reduce 方法中重构了你的代码

const myArray = [
  { group: 'groupA', message: 'Text without a number', sl: '1A' },
  { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupB', message: 'Text without a number', sl: '1A' },
  { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupB', message: 'Text with a number WO5467829', sl: '1A' },
  { group: 'groupC', message: 'Text without a number', sl: '1B' },
  { group: 'groupD', message: 'Text with a number Tick0127866', sl: '1B' },
  { group: 'groupC', message: 'Text without a number', sl: '1A' }
];

let output = myArray.reduce((acc, line) => {
  acc[line.group] = acc[line.group] || {verified: 0, unverified: 0};
  if(line.message.match(/\d{6,}/)){
    acc[line.group].verified++
  }
  else{
    acc[line.group].unverified++
  }

  return acc;
}, {});

output = Object.entries(output).map(([k, v]) => ({group: k, ...v}))

console.log('output', output);

【讨论】：

有人似乎对这里的所有答案都投了反对票。

【解决方案6】：

像这样将 reduce 与正则表达式测试结合使用 -

const myArray = [{
    group: 'groupA',
    message: 'Text without a number',
    sl: '1A'
  },
  {
    group: 'groupA',
    message: 'Text with a number WO5467829',
    sl: '1A'
  },
  {
    group: 'groupB',
    message: 'Text without a number',
    sl: '1A'
  },
  {
    group: 'groupA',
    message: 'Text with a number WO5467829',
    sl: '1A'
  },
  {
    group: 'groupB',
    message: 'Text with a number WO5467829',
    sl: '1A'
  },
  {
    group: 'groupC',
    message: 'Text without a number',
    sl: '1B'
  },
  {
    group: 'groupD',
    message: 'Text with a number Tick0127866',
    sl: '1B'
  },
  {
    group: 'groupC',
    message: 'Text without a number',
    sl: '1A'
  }
];

const numberRegex = /[0-9]{6}/;

const res = Object.values(myArray.reduce((acc, curr) => {
  const { group, message } = curr;
  const isPhoneVerified = numberRegex.test(message);

  if (!acc[group] && isPhoneVerified) {
    acc[group] = { group: group, verified: 1, unverified: 0 };
  } else if (!acc[group] && !isPhoneVerified) {
    acc[group] = { group: group, verified: 0, unverified: 1 };
  } else if (acc[group] && isPhoneVerified) {
    acc[group].verified += 1;
  } else if (acc[group] && !isPhoneVerified) {
    acc[group].unverified += 1;
  }

  return acc;

}, {}));

console.log(res);

【讨论】：