Javascript Lodash 按外部数组和内部属性排序

Question

I have an array of people that I need to sort by a defined external array (order) and then by age. I am using lodash sortBy

const _  = require('lodash');
const arr = [
  { name: "Mandy", age: "34" },
  { name: "Shelly", age: "32" },
  { name: "Kyle", age: "12" },
  { name: "Kyle", age: "60" },
  { name: "Mandy", age: "32" },
  { name: "Mandy", age: "99" },
  { name: "Shelly", age: "30" },
  { name: "John", age: "3" },
  { name: "John", age: "1" },
  { name: "John", age: "6" },
  { name: "Mandy", age: "3" }
];

let order = ["Shelly", "John", "Mandy", "Kyle"];

let sortedArrByOrder = _.sortBy(arr, [person => order.indexOf(person.name), 'age'], ['asc', 'desc']);

console.log(sortedArrByOrder);

But the age is not sorted in desc order. Is there a way to make it work?

Answer 1

The _.sortBy() doesn't except order (asc / desc), use _.orderBy() instead:

 const arr = [{ name: "Mandy", age: "34" },{ name: "Shelly", age: "32" },{ name: "Kyle", age: "12" },{ name: "Kyle", age: "60" },{ name: "Mandy", age: "32" },{ name: "Mandy", age: "99" },{ name: "Shelly", age: "30" },{ name: "John", age: "3" },{ name: "John", age: "1" },{ name: "John", age: "6" },{ name: "Mandy", age: "3" }]; const order = ["Shelly", "John", "Mandy", "Kyle"]; const sortedArrByOrder = _.orderBy(arr, [person => order.indexOf(person.name), 'age'], ['asc', 'desc']); console.log(sortedArrByOrder);

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

In addition, using Array.indexOf() (O(n)) inside a sort operation (O(nLogn) for array with more than 10 items), might hurt the performance. A better way would be to convert the order array to a data structure with O(1) retrieval like an Map or plain object, and store the original index from the array. Now you can get the original index directly:

 const arr = [{ name: "Mandy", age: "34" },{ name: "Shelly", age: "32" },{ name: "Kyle", age: "12" },{ name: "Kyle", age: "60" },{ name: "Mandy", age: "32" },{ name: "Mandy", age: "99" },{ name: "Shelly", age: "30" },{ name: "John", age: "3" },{ name: "John", age: "1" },{ name: "John", age: "6" },{ name: "Mandy", age: "3" }]; const order = new Map(["Shelly", "John", "Mandy", "Kyle"].map((s, i) => [s, i])) const sortedArrByOrder = _.orderBy(arr, [person => order.get(person.name), 'age'], ['asc', 'desc']); console.log(sortedArrByOrder);

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

Answer 2

You could take a callback and return the negative age and omit the array for the order.

 const arr = [{ name: "Mandy", age: "34" }, { name: "Shelly", age: "32" }, { name: "Kyle", age: "12" }, { name: "Kyle", age: "60" }, { name: "Mandy", age: "32" }, { name: "Mandy", age: "99" }, { name: "Shelly", age: "30" }, { name: "John", age: "3" }, { name: "John", age: "1" }, { name: "John", age: "6" }, { name: "Mandy", age: "3" }], order = ["Shelly", "John", "Mandy", "Kyle"], sortedArrByOrder = _.sortBy(arr, [ ({ name }) => order.indexOf(name), ({ age }) => -age ]); console.log(sortedArrByOrder);

 .as-console-wrapper { max-height: 100%;important: top; 0; }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>

Answer 3

You can do this with sort method in plain javascript with ||operator. So you first sort by order and then by age .

 const arr = [{ name: "Mandy", age: "34" },{ name: "Shelly", age: "32" },{ name: "Kyle", age: "12" },{ name: "Kyle", age: "60" },{ name: "Mandy", age: "32" },{ name: "Mandy", age: "99" },{ name: "Shelly", age: "30" },{ name: "John", age: "3" },{ name: "John", age: "1" },{ name: "John", age: "6" },{ name: "Mandy", age: "3" }]; const order = ["Shelly", "John", "Mandy", "Kyle"]; arr.sort((a, b) => order.indexOf(a.name) - order.indexOf(b.name) || b.age - a.age) console.log(arr)