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在数组中查找最近的日期

date function arrays html javascript

Harper Creek · 技术社区 · 7 年前

我试图在一系列具有不同日期的对象中找到最高日期,这些日期将归属于每个对象。只要日期在1970年1月1日以上,代码就工作得很好,但在此之前的任何日期都会导致错误。我怎么能用同样的日期来解决呢?我知道我可以利用所有的日期(时间),但有什么办法吗?谢谢。

var playerData = [
    {name: "John"},
    {name: "Bill"},
    {name: "Bob"},
    {name: "Jim"},
    
];
    
var dateOne = new Date(1940,02,05);
var dateTwo = new Date(1950, 06,18);
var dateThree = new Date(1650,07,12);
var dateFour = new Date(1300, 03,25);
    
playerData[0].date = dateOne;
playerData[1].date = dateTwo;
playerData[2].date = dateThree;
playerData[3].date = dateFour;

function findHighDate() {
    var highDateSoFar = null;
    var result;
    for (var i = 0; i < playerData.length; i++) {
        if (playerData[i].date > highDateSoFar) {
            result = playerData[i];
            highDateSoFar = playerData[i].date;
        }
        else if (playerData[i].date === highDateSoFar) {	
            result = 'equal';
        
    }
    }
    return result;
}
    
var highPlayer = findHighDate();
var highPlayerName = highPlayer.name;
var highPlayerIndex = playerData.indexOf(highPlayer);
var highPlayerDate = highPlayer.date;
console.log({highPlayer},{highPlayerIndex},{highPlayerName},{highPlayerDate});

5 回复 | 直到 7 年前

jo_va 7 年前

您可以比较字符串并使用 Array.sort 要按降序排列,请获取第一项:

const playerData = [
  {name: "John", date: '1940-02-05' },
  {name: "Bill", date: '1950-06-18' },
  {name: "Bob", date: '1650-07-12' },
  {name: "Jim", date: '1300-03-25' },
];

function findHighDate() {
  return playerData.sort((a, b) => b.date.localeCompare(a.date))[0];
}
    
const highPlayer = findHighDate();
const highPlayerName = highPlayer.name;
const highPlayerIndex = playerData.indexOf(highPlayer);
const highPlayerDate = new Date(highPlayer.date);
console.log({ highPlayer, highPlayerIndex, highPlayerName, highPlayerDate });

或者你也可以坚持使用日期并使用 Date.getTime() 排序数组:

const playerData = [
  {name: "John", date: new Date('1940-02-05') },
  {name: "Bill", date: new Date('1950-06-18') },
  {name: "Bob", date: new Date('1650-07-12') },
  {name: "Jim", date: new Date('1300-03-25') },
];

function findHighDate() {
  return playerData.sort((a, b) => b.date.getTime() - a.date.getTime())[0];
}
    
const highPlayer = findHighDate();
const highPlayerName = highPlayer.name;
const highPlayerIndex = playerData.indexOf(highPlayer);
const highPlayerDate = highPlayer.date;
console.log({ highPlayer, highPlayerIndex, highPlayerName, highPlayerDate });

正如@Scott Sauyet在下面的评论中指出的,使用 Array.sort 对你的场景来说可能是太过分了。

你可以找到你的最高日期与多一点的代码和帮助 reduce :

const playerData = [
  {name: "John", date: new Date('1940-02-05') },
  {name: "Bill", date: new Date('1950-06-18') },
  {name: "Bob", date: new Date('1650-07-12') },
  {name: "Jim", date: new Date('1300-03-25') },
];

function findHighDate() {
  return playerData.reduce((highest, player) => {
    return highest.date.getTime() > player.date.getTime() ? highest : player;
  }, playerData[0]);
}
    
const highPlayer = findHighDate();
const highPlayerName = highPlayer.name;
const highPlayerIndex = playerData.indexOf(highPlayer);
const highPlayerDate = highPlayer.date;
console.log({ highPlayer, highPlayerIndex, highPlayerName, highPlayerDate });

Badabomb 7 年前

var playerData = [
    {name: "John"},
    {name: "Bill"},
    {name: "Bob"},
    {name: "Jim"},

];

var dateOne = new Date(1940,02,05);
var dateTwo = new Date(1950, 06,18);
var dateThree = new Date(1650,07,12);
var dateFour = new Date(1300, 03,25);

playerData[0].date = dateOne;
playerData[1].date = dateTwo;
playerData[2].date = dateThree;
playerData[3].date = dateFour;

function findHighDate() {
    console.log(playerData);
    var highDateSoFar = playerData[0].date;
    var result = playerData[0];
    for (var i = 0; i < playerData.length; i++) {
        if (playerData[i].date > highDateSoFar) {
            result = playerData[i];
            highDateSoFar = playerData[i].date;
        }
        else if (playerData[i].date === highDateSoFar) {    

    }
    }
    return result;
}

var highPlayer = findHighDate();
var highPlayerName = highPlayer.name;
var highPlayerIndex = playerData.indexOf(highPlayer);
var highPlayerDate = highPlayer.date;
console.log({highPlayer},{highPlayerIndex},{highPlayerName},{highPlayerDate});

Matt Way 7 年前

如果你使用 getTime() 在日期上,1970年之前的数字将是负数,所以通常的数学比较很有效。下面我简单地按日期对你的播放器数据进行排序(最大值优先)。如果想要最高的,只需抓取数组中的第一项:

var playerData = [
  {name: "John"},
  {name: "Bill"},
  {name: "Bob"},
  {name: "Jim"},   
]
    
playerData[0].date = new Date(1940, 02, 05)
playerData[1].date = new Date(1950, 06, 18)
playerData[2].date = new Date(1650, 07, 12)
playerData[3].date = new Date(1300, 03, 25)

playerData.sort((a, b) => b.date.getTime() - a.date.getTime())

console.log(playerData)

dabishan 7 年前

var playerData = [
    {name: "John"},
    {name: "Bill"},
    {name: "Bob"},
    {name: "Jim"},
    
];
    
var dateOne = new Date(1940,02,05);
var dateTwo = new Date(1950, 06,18);
var dateThree = new Date(1650,07,12);
var dateFour = new Date(1300, 03,25);
    
playerData[0].date = dateOne;
playerData[1].date = dateTwo;
playerData[2].date = dateThree;
playerData[3].date = dateFour;

function playerWithHighestDate() {
	// start by assuming player 0 is highest
    var winner = 0;
    
    // start at one as we dont need to compare with player 0
    for (var i = 1; i < playerData.length; i++) {
    		// compares players date
        if (playerData[i].date >= playerData[winner].date) {
            winner = i;
        }
    }
    
    // returns the winner index
    return winner;
}

// get index with highest date
var highPlayerIndex = playerWithHighestDate();
var highPlayer = playerData[highPlayerIndex];
var highPlayerName = highPlayer.name;
var highPlayerDate = highPlayer.date;
console.log({highPlayer},{highPlayerIndex},{highPlayerName},{highPlayerDate});

RobG 7 年前

使用 > 因为与数字的共回归在大多数情况下都是有效的,然而当与数字进行比较时计算结果为0,因此负数小于 .

所以只要通过初始化 截止日期 或者测试它是否存在 无效的

var playerData = [
    {name: "John", date: new Date(1940, 2,  5)},
    {name: "Bill", date: new Date(1950, 6, 18)},
    {name: "Bob",  date: new Date(1650, 7, 12)},
    {name: "Jim",  date: new Date(1300, 3, 25)},
];

function findHighDate(data) {
  var highDateSoFar = null; 
  var result;
  
  for (var i=0; i < data.length; i++) {

    if (highDateSoFar === null || data[i].date > highDateSoFar) {
      result = data[i];
      highDateSoFar = data[i].date;
    }
  }
  return result ;
}

console.log( findHighDate(playerData) );

还有表达式 playerData[i].date === highDateSoFar 和 截止日期 引用相同的日期对象,这在函数的逻辑中不可能是真的。

减少对于这一点:

var playerData = [
  {name: "John", date: new Date(1940, 2,  5)},
  {name: "Bill", date: new Date(1950, 6, 18)},
  {name: "Bob",  date: new Date(1650, 7, 12)},
  {name: "Jim",  date: new Date(1300, 3, 25)},
];

function getHighest(data) {
  return data.reduce((acc, high) => {
     acc = high.date > acc.date? high : acc;
     return acc;
  }, {date:-Infinity});
}

console.log(getHighest(playerData));

Scott Sauyet 7 年前

我经常发现,通过提升一两个抽象层次来解决问题更容易。如果我们想找到具有最高date属性的对象,我可以先写一些东西,通过任何给定的属性找到最大值。但更好的是,我可以给它提供一个函数,并找到使函数最大化的值。事实证明,这和date一样容易写,而且它将寻找最大值的逻辑与选择date属性的普通逻辑分离开来。

所以我们可以在这里写作

const maximumBy = (fn) => (data) => 
  data.reduce((m, x) => fn(x) > fn(m) ? x : m, data[0])

const findHighestPlayer = maximumBy(player => player.date)

var playerData = [
    {name: "John", date: new Date(1940, 2,  5)},
    {name: "Bill", date: new Date(1950, 6, 18)},
    {name: "Bob",  date: new Date(1650, 7, 12)},
    {name: "Jim",  date: new Date(1300, 3, 25)},
];


console.log(findHighestPlayer(playerData))

请注意,如果数组为空,则返回 undefined ,但很难知道还能做什么。如果需要修复的话,您可以添加一个默认值参数。