javascript - 重新组织对象的javascript数组

Question

我有一系列问题和不同的答案(我是动态构建的，所以条目的数量和不同的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"},
]

我需要一个函数来由此构建另一个数组对象，该对象将包含“answer”和“count”，在本例中为:

[
    { 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，而无需直接循环？

Answer 1

如果 ES6 没有问题，可以通过:

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);