Get 5 oldest Objects from an array-CodePudding

I have an array of objects of the form:

{productID: '15', name: 'Pepsi', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z'}

I want to find the 5 oldest items by comparing the dateAdded strings. I have tried a few inefficient loops and failed with reduce(), but I feel there's a more efficient way. How can I accumulate the 5 oldest items?

CodePudding user response：

a simple sort/slice will do it - the format of the date means you can just do a localeCompare in your sort callack ... `

const array = [
    {productID: '15',name: 'Pepsi',category: 'food/beverages',dateAdded: '2015-12-21T17:42:34Z'},
    {productID: '13',name: 'Coke',category: 'food/beverages',dateAdded: '2015-12-20T17:42:34Z'}
];
const top5 = array
    .sort(({dateAdded: a}, {dateAdded: b}) => a.localeCompare(b))
    .slice(0, 5);
console.log(top5);

CodePudding user response：

Sort the items by dateAdded then take the top 5, which should be the oldest

CodePudding user response：

Sort by datetime

const array = [
  { productID: '0', name: 'Pepsi', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '1', name: 'Coke', category: 'food/beverages', dateAdded: '2015-10-20T17:42:34Z' },
  { productID: '2', name: 'Coke', category: 'food/beverages', dateAdded: '2015-11-20T17:42:34Z' },
  { productID: '3', name: 'Coke', category: 'food/beverages', dateAdded: '2015-08-20T17:42:34Z' },
  { productID: '4', name: 'Coke', category: 'food/beverages', dateAdded: '2015-01-20T17:42:34Z' },
  { productID: '5', name: 'Coke', category: 'food/beverages', dateAdded: '2015-03-20T17:42:34Z' },
  { productID: '6', name: 'Coke', category: 'food/beverages', dateAdded: '2016-10-20T17:42:34Z' },
  { productID: '7', name: 'Coke', category: 'food/beverages', dateAdded: '2017-10-20T17:42:34Z' },
];

const newArr = array.sort((firstEl, secondEl) => new Date(firstEl.dateAdded).getTime() - new Date(secondEl.dateAdded).getTime()).slice(0, 5)

console.log(newArr)

CodePudding user response：

const oldest = (arr) => arr.sort((a, b) => new Date(a.dateAdded) - new Date(b.dateAdded)).slice(0, 5)
const products = [
  { productID: '15', name: 'Pepsi', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '16', name: 'Coke', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '17', name: 'Sprite', category: 'food/beverages', dateAdded: '2014-12-21T17:42:34Z' },
  { productID: '18', name: 'Fanta', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '19', name: 'Dr Pepper', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '20', name: 'Mountain Dew', category: 'food/beverages', dateAdded: '2012-12-21T17:42:34Z' },
  { productID: '21', name: 'Diet Coke', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '22', name: '7up', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '23', name: 'Cherry Coke', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '24', name: 'Cherry Coke Zero', category: 'food/beverages', dateAdded: '2010-12-21T17:42:34Z' },
  { productID: '25', name: 'Cherry Coke Diet', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '26', name: 'Cherry Coke Diet Zero', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '27', name: 'Cherry Coke Diet Zero', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '28', name: 'Cherry Coke Diet Zero', category: 'food/beverages', dateAdded: '2011-12-21T17:42:34Z' },
  { productID: '29', name: 'Cherry Coke Diet Zero', category: 'food/beverages', dateAdded: '2015-12-21T17:42:34Z' },
  { productID: '30', name: 'Cherry Coke Diet Zero', category: 'food/beverages', dateAdded: '2014-12-21T17:42:34Z' }]
console.log(oldest(products));