Question

我有一系列问题和不同的答案（我是动态构建的，因此条目数和不同答案可能会有所不同）：

var qaArray = [
    { question: "Question", answer: "Answer A"},
    { question: "Question", answer: "Answer B"},
    { question: "Question", answer: "Answer B"},
    { question: "Question", answer: "Answer C"},
    { question: "Question", answer: "Answer A"},
    { question: "Question", answer: "Answer B"},
    { question: "Question", answer: "Answer C"},
    { question: "Question", answer: "Answer A"},
    { question: "Question", answer: "Answer B"},
]

我需要一个函数来构建另一个数组对象，这将保留答案＆＃39;和＆＃39;计算＆＃39;，在这种情况下它将是：

[
    { answer: "Answer A", count: 3 },
    { answer: "Answer B", count: 4 },
    { answer: "Answer C", count: 2 },
]

有没有一种简单的方法可以做到这一点，没有直接循环？

Answer 1

如果ES6不是问题，可以通过以下方式完成：

var qaArray = [
    { question: "Question", answer: "Answer A"},
    { question: "Question", answer: "Answer B"},
    { question: "Question", answer: "Answer B"},
    { question: "Question", answer: "Answer C"},
    { question: "Question", answer: "Answer A"},
    { question: "Question", answer: "Answer B"},
    { question: "Question", answer: "Answer C"},
    { question: "Question", answer: "Answer A"},
    { question: "Question", answer: "Answer B"},
];

var result = [...new Set(qaArray.map(q => q.answer))].map(a => ({ answer: a, count: qaArray.filter(e => e.answer === a).length }));

console.log(result);

Answer 2

如果您正在寻找没有reduce或forEach的解决方案，请使用lodash进行详细说明。

_.countBy会为您提供贴近的结果，但如果您想根据需要将其转换为数组，请使用mapValues。

_.chain(qaArray)
.countBy('answer')
.mapValues(function(value, key) {
  return { answer: key, count: value }
})
.values()
.value()

Answer 3

您可以使用reduce。如果元素不存在则将元素推送到累加器，如果存在则递增count。

请找到以下解决方案

＆＃13;

var qaArray = [
    { question: "Question", answer: "Answer A"},
    { question: "Question", answer: "Answer B"},
    { question: "Question", answer: "Answer B"},
    { question: "Question", answer: "Answer C"},
    { question: "Question", answer: "Answer A"},
    { question: "Question", answer: "Answer B"},
    { question: "Question", answer: "Answer C"},
    { question: "Question", answer: "Answer A"},
    { question: "Question", answer: "Answer B"},
]


result = qaArray.reduce((acc, item) => {
  var exist = acc.find(x => x.answer === item.answer);
  if (exist) {
    exist.count += 1;
  } else {
    acc.push({
      answer: item.answer,
      count: 1
    })
  }
  return acc;
}, []);


console.log(result);

＆＃13;

Answer 4

您可以使用Map来确定答案，然后reduce对数据进行处理以获取计数，如下所示：

var result = Array.from(qaArray.reduce((acc, { answer }) => {
  const current = acc.get(answer) || { answer, count: 0 };
  current.count++;
  return acc.set(answer, current);
}, new Map()).values());

console.log(result);

重新组织javascript对象数组

4 个答案: