Question

我得到一个输入= 5。

我想将此数组中5个随机对象的is_winner键设置为true。

const participants = [
    {code: '111111', is_winner: false},
    {code: '222222', is_winner: false},
    {code: '444444', is_winner: false},
    {code: '777777', is_winner: false},
    {code: '555555', is_winner: false},
    {code: '666666', is_winner: false},
    {code: '333333', is_winner: false},
    {code: '888888', is_winner: false},
    {code: '999999', is_winner: false},
];

第一次随机分组：

const participants = [
    {code: '111111', is_winner: false},
    {code: '222222', is_winner: true},
    {code: '444444', is_winner: false},
    {code: '777777', is_winner: true},
    {code: '555555', is_winner: false},
    {code: '666666', is_winner: true},
    {code: '333333', is_winner: true},
    {code: '888888', is_winner: false},
    {code: '999999', is_winner: true},
];

我尝试了以下具有2个for循环的循环，其中之一是O（n ^ 2）

const winners = [];

while (winners.length < 5) {
    const randomParticipant = participants[Math.floor(Math.random() * participants.length)];

    if (!winners.includes(randomParticipant.code)) {
        winners.push(randomParticipant.code);
    }
}

for (let participant of participants) {
    if (winners.includes(participant.code)) {
        participant.is_winner = true;
    }
}

希望看看是否有更有效的方法。

Answer 1

您还可以考虑像这样使用Set和Array.forEach来做到这一点：

const participants = [ {code: '111111', is_winner: false}, {code: '222222', is_winner: false}, {code: '444444', is_winner: false}, {code: '777777', is_winner: false}, {code: '555555', is_winner: false}, {code: '666666', is_winner: false}, {code: '333333', is_winner: false}, {code: '888888', is_winner: false}, {code: '999999', is_winner: false}, ];

let randomize = (arr, n=5, clone=true) => {
  let set = new Set(), _arr = arr
  if(clone) _arr = arr.map(x => ({...x})) // skip if you want to mutate
  while(set.size < n) set.add(Math.floor(Math.random() * participants.length))
  Array.from(set).forEach(x => _arr[x].is_winner = true)
  return _arr
}

console.log(randomize(participants))
console.log(randomize(participants, 3))

Set和while负责生成随机数数组（在您的情况下为数组索引）。有了该功能后，您只需通过is_winner将true设置为Array.forEach。

因为函数最好不要改变输入，所以我添加了clone标志，但是如果您不关心它，可以将其删除，也可以删除if(clone)行（仅创建一个克隆）的数组。

Answer 2

// Found a nice way to shuffle in this SOF post https://stackoverflow.com/questions/6274339/how-can-i-shuffle-an-array
const shuffle = (array) => {
    for (let i = array.length - 1; i > 0; i--) {
        let j = Math.floor(Math.random() * (i + 1));
        [array[i], array[j]] = [array[j], array[i]];
    }
    return array
};

// Selects random participants and set their is_winner key to true.
const setRandomWinners = (numberOfWinners) => {
    const arr = [...Array(participants.length).keys()];
    const shuffledArr = shuffle(arr);
    const newArr = shuffledArr.slice(0, numberOfWinners);

    for (let el of newArr) {
        participants[el].is_winner = true;
    }
};

将随机对象的关键点设置为其他值

2 个答案: