如何获取对象内数组元素的索引？

Question

const questions = [
    {
      "question": "What is the scientific name of a butterfly?",
      "answers": ["Apis", "Coleoptera", "Formicidae", "Rhopalocera"],
      "correctIndex": 3
    },
    {
      "question": "How hot is the surface of the sun?",
      "answers": ["1,233 K", "5,778 K", "12,130 K", "101,300 K"],
      "correctIndex": 1
    },
]

我正在尝试这种方式，但是 return -1:

console.log(questions.findIndex(value => value.answers.indexOf() === 'Apis'));

例如，如果想获得 indexOf 'Apis'，我得到 -1。

我正在尝试比较 'CorrectIndex' 值与答案数组值的索引以及 return 是否正确。

Answer 1

你为什么要比较value.answers.indexOf()

正确的语法应该是

console.log(questions.findIndex(value => value.answers.indexOf('element')));

Answer 2

您只是错误地使用了 indexOf。这很容易修复：

const questions = [
    {
      question: "What is the scientific name of a butterfly?",
      answers: ["Apis", "Coleoptera", "Formicidae", "Rhopalocera"],
      correctIndex: 3
    },
    {
      question: "How hot is the surface of the sun?",
      answers: ["1,233 K", "5,778 K", "12,130 K", "101,300 K"],
      correctIndex: 1
    }
]

questions.forEach(question => {
  console.log(question.answers.indexOf('Apis'))
});

意识到 indexOf 是一个函数并接收一个字符串。

Answer 3

如果我没理解错的话，你想获取这个对象的answers数组中元素的索引。试试这个：

console.log(questions.map(value => value.answers.indexOf('Apis')));

这将为您提供一个值为“Apis”的索引数组。

如果同一个数组中有重复值，可以这样做：

console.log(questions.map(value => [value.answers.indexOf('Apis')]));

这将存储一个数组的数组，您可以在其中获取每个对象的“Apis”的索引。

I'm trying to compare 'CorrectIndex' value with index of answers array value and return if its correct or not.

试试这个

const questions = [
    {
      "question": "What is the scientific name of a butterfly?",
      "answers": ["Apis", "Coleoptera", "Formicidae", "Rhopalocera"],
      "correctIndex": 3
    },
    {
      "question": "How hot is the surface of the sun?",
      "answers": ["1,233 K", "5,778 K", "12,130 K", "101,300 K"],
      "correctIndex": 1
    },
]

console.log(questions.map(value => value.answers.indexOf('Apis') === value.correctIndex));

如何获取对象内数组元素的索引？

How can I get the index of array element inside object?

javascript

html

indexof

试试这个