如何从Javascript中的旧数组中获取包含一些随机元素的新数组 [英] How to get a new array containing some random elements from an old array in Javascript

问题描述

我正在用 React Native 制作一个测验应用程序，它有这个对象数组，其中每个对象都包含一个问题陈述、选择和正确的选择.这里总共有 15 个对象，但我需要一个新数组，其中只包含这个数组的 5 个对象.每次我开始测验时都应该随机选择它们.如何获取该数组，帮助

I am making a quiz app in react native, it has this array of objects in which each object contains a question statement,choices and the correct choice. There will be total 15 objects in this, but i require a new array that contains only 5 of the objects of this array. They should be selected at random everytime i start the quiz. How to get that array, help

const questions = [
    new quizQuestions(
        'What is capital of Pakistan?',
        ['Karachi', 'Islamabad', 'Lahore', 'Peshawar'],
        'Islamabad',
    ),
    new quizQuestions(
        'What is capital of India?',
        ['delhi', 'Islamabad', 'zcjzj', 'Peshawar'],
        'delhi',
    ),
    new quizQuestions(
        'What is capital of Pakistan?',
        ['Karachi', 'Islamabad', 'Lahore', 'Peshawar'],
        'Islamabad',
    ),
]

推荐答案

您需要的非常随意.

使用生成器函数:

const questions = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
function* randomise(arr, numOfElem) {
  // Create a copy of question so that wont effect actual array
  let copyArray = [...arr];

  // Use copyArray to generate random as closure, so that it never go out of index
  const getRandom = () => Math.floor(Math.random() * copyArray.length);
  // This is generator function run always
  while (true) {
    // If numOfElem is greater, then clone again

    // suppose you have 15 question but you take 6. SO after 2 iteration, copyArray will have only 3 element so clone again
    if (numOfElem > copyArray.length) {
      // Clone again
      copyArray = [...arr];
    }
    // pick 5 random data.
    let result = [];
    for (let i = 0; i < numOfElem; i++) {
      result.push(copyArray.splice(getRandom(), 1)[0]);
    }
    yield result;
  }
}

const questionGenerator = randomise(questions, 5);
console.log(questionGenerator.next().value); // random [ 11, 3, 7, 2, 8 ]

console.log(questionGenerator.next().value); // random [ 12, 13, 14, 9, 5 ]

console.log(questionGenerator.next().value); // random [ 6, 1, 4, 15, 10 ]

console.log(questionGenerator.next().value); // random [ 14, 12, 8, 2, 13 ]

console.log(questionGenerator.next().value); // random [ 9, 3, 10, 6, 11 ]

相同但没有生成器函数.

const questions = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
const randomise = (arr, numOfElem) => {
  let copyArray = [...arr];
  const getRandom = () => Math.floor(Math.random() * copyArray.length);
  return () => {
    // If numOfElem is greater, then clone again

    // suppose you have 15 question but you take 6. SO after 2 iteration, copyArray will have only 3 element so clone again
    if (numOfElem > copyArray.length) {
      // Clone again
      copyArray = [...arr];
    }
    // pick 5 random data.
    let result = [];
    for (let i = 0; i < numOfElem; i++) {
      result.push(copyArray.splice(getRandom(), 1)[0]);
    }
    return result;
  };
};
const questionGenerator = randomise(questions, 5);
console.log(questionGenerator()); // random [ 11, 3, 7, 2, 8 ]

console.log(questionGenerator()); // random [ 12, 13, 14, 9, 5 ]

console.log(questionGenerator()); // random [ 6, 1, 4, 15, 10 ]

console.log(questionGenerator()); // random [ 14, 12, 8, 2, 13 ]

console.log(questionGenerator()); // random [ 9, 3, 10, 6, 11 ]

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