迭代数组并将唯一参数添加到新数组答案

【问题标题】：Iterating over array and adding unique parameters to new array迭代数组并将唯一参数添加到新数组
【发布时间】：2018-01-17 13:22:11
【问题描述】：

我遇到了一个问题，希望得到有关如何解决的反馈。

这是我的 JSON：

  questions: [
    {
      question: 'lala',
      answer: 'papa',
      categories: ['Handla']

    },
    {
      question: 'xxxx',
      answer: 'yyyy',
      categories: ['Reklamation']
    },
    {
      question: 'abcefg',
      answer: 'gooooogle',
      categories: ['Reklamation']
    }
  ]

我想遍历这个问题数组并将 ALL object.categories 附加到一个新数组，然后过滤掉重复的数组。所以基本上我的回答应该是：

["Handla", "Reklamation"]

【问题讨论】：

根本不是很好的复制品。这是可能的解决方案：const categories = data.questions.reduce((prev, curr) => prev.concat(curr.categories), []).filter((category, index, array) => array.indexOf(category) === index).
@dfsq 这比vars cats=[]; for (var i = 0; i < questions.length; i++) { var cat = questions[i].categories[0]; if (cats.indexOf(cat) == -1) cats.push(cat); } 更漂亮、更易读——我眼里含着泪；）

标签： javascript arrays ecmascript-6

【解决方案1】：

感谢 ES6 Set，您可以轻松过滤重复值。您只需先将类别展平为一个数组：

const questions = [
    {
      question: 'lala',
      answer: 'papa',
      categories: ['Handla']

    },
    {
      question: 'xxxx',
      answer: 'yyyy',
      categories: ['Reklamation']
    },
    {
      question: 'abcefg',
      answer: 'gooooogle',
      categories: ['Reklamation']
    }
  ];
const flattened = questions.reduce((prev, curr) => [...prev, ...curr.categories], []); // ['Handla', 'Reklamation', 'Reklamation']
const unique = Array.from(new Set(flattened));
console.log(unique);

【讨论】：

【解决方案2】：

您可以使用 map() 方法和 ES6 Set 和扩展语法 ... 来做到这一点

const data = {"questions":[{"question":"lala","answer":"papa","categories":["Handla"]},{"question":"xxxx","answer":"yyyy","categories":["Reklamation"]},{"question":"abcefg","answer":"gooooogle","categories":["Reklamation"]}]}

const result = [...new Set([].concat(...data.questions.map(o => o.categories)))]
console.log(result)

或者代替map()，您可以使用reduce() 并使用Set 作为累加器参数。

const data = {"questions":[{"question":"lala","answer":"papa","categories":["Handla"]},{"question":"xxxx","answer":"yyyy","categories":["Reklamation"]},{"question":"abcefg","answer":"gooooogle","categories":["Reklamation"]}]}

const result = [...data.questions.reduce((r, e) => {
  return r.add(...e.categories), r
}, new Set)]
console.log(result)

【讨论】：

【解决方案3】：

您可以分两步完成。将问题减少到所有类别的数组，然后过滤独特的项目。像这样的：

const data = {
  questions: [{
      question: 'lala',
      answer: 'papa',
      categories: ['Handla']

    },
    {
      question: 'xxxx',
      answer: 'yyyy',
      categories: ['Reklamation']
    },
    {
      question: 'abcefg',
      answer: 'gooooogle',
      categories: ['Reklamation']
    }
  ]
}

const categories = data.questions
  .reduce((prev, curr) => prev.concat(curr.categories), [])
  .filter((category, index, array) => array.indexOf(category) === index)

console.log(categories)

【讨论】：

【解决方案4】：

您可以将所有类别收集到一个数组中，并使用Set 获取唯一值。

var questions= [{ question: 'lala', answer: 'papa', categories: ['Handla'] }, { question: 'xxxx', answer: 'yyyy', categories: ['Reklamation'] }, { question: 'abcefg', answer: 'gooooogle', categories: ['Reklamation'] }],
    unique = [...new Set(questions.reduce((r, { categories: c }) => r.concat(c), []))];
  
console.log(unique);

【讨论】：

【解决方案5】：

您可以在更多浏览器上使用普通的旧 JS

var cats = [], questions = [{question: 'lala',answer: 'papa',categories: ['Handla']},{question: 'xxxx',answer: 'yyyy',categories: ['Reklamation']},{question: 'abcefg',answer: 'gooooogle',categories: ['Reklamation']}];

for (var i = 0; i < questions.length; i++) {
  var cat = questions[i].categories[0];
  if (cats.indexOf(cat) == -1) cats.push(cat);
}
console.log(cats);

更现代一点：

const questions = [{question: 'lala',answer: 'papa',categories: ['Handla']},{question: 'xxxx',answer: 'yyyy',categories: ['Reklamation']},{question: 'abcefg',answer: 'gooooogle',categories: ['Reklamation']}];
let cats = [];

questions.forEach(function(q) {
  var cat = q.categories[0];
  if (cats.indexOf(cat) == -1) cats.push(cat);
});
console.log(cats);

【讨论】：