如何根据最大键获取对象中的值（Date is an Key）

Question

我将对象的日期作为键，将值作为位置。我想根据最大日期获取位置。这里的位置是相同的。日期键采用 "MM/DD/YYYY" 格式。

var obj ={};
    obj['9/10/2016'] = "India-Chennai";
    obj['9/15/2016'] = "Australia-Melborne";
    obj['9/20/2016'] = "India-Delhi";
    obj['9/25/2016'] = "India-Chennai";

从上面的对象中最大的 Date(Key) 是 "9/25/2016" 值是 "India-Chennai" 如何根据最大的键获取值？

提前致谢

Answer 1

你可能会这样做；

var obj = {},
 latest = [];
  obj['9/20/2016'] = "India-Delhi";
  obj['9/10/2016'] = "Japan-Osaka";
  obj['9/25/2016'] = "India-Chennai";
  obj['9/15/2016'] = "Australia-Melborne";
  
 latest = obj[Object.keys(obj).sort((a,b) => new Date(b).getTime() - new Date(a).getTime())[0]];
 console.log(latest);

Answer 2

您可以使用 Object.keys()、Array.prototype.map()、Math.max()、Date.prototype.getTime()、Array.prototype.indexOf()

var obj = {};
obj['9/10/2016'] = "India-Chennai";
obj['9/15/2016'] = "Australia-Melborne";
obj['9/20/2016'] = "India-Delhi";
obj['9/25/2016'] = "India-Chennai";

var keys = Object.keys(obj);
var map = keys.map(function(date) {return new Date(date).getTime()});
var key = Math.max.apply(Math, map);
var value = obj[keys[map.indexOf(key)]];

console.log(value);

Answer 3

您可以使用 Object.keys() 获取键列表作为数组，然后 .sort() 该数组：

var obj ={};
obj['9/10/2016'] = "India-Chennai";
obj['9/9/2016'] = "Australia-Melborne";
obj['9/25/2016'] = "India-Chennai";
obj['9/20/2016'] = "India-Delhi";
    
var parseDate = d => (d = d.match(/(\d{1,2})\/(\d{1,2})\/(\d{4})/)) && new Date(d[3],d[1]-1,d[2]);
var latestKey = Object.keys(obj).sort((a, b) => parseDate(a) - parseDate(b)).pop();
var result = obj[latestKey];

console.log(latestKey, result);

我使用了正则表达式来解析日期，这样代码就可以很容易地适应其他日期格式，例如，如果您需要 d/m/yyyy 而不是 m/d/yyyy。

如何根据最大键获取对象中的值（Date is an Key）

How to get the value in object based on the largest key (Date is an Key)

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