Lodash / JS orderBy与嵌套的空值

Question

My question is kinda linked to this one, but one step more complex : lodash orderby with null and real values not ordering correctly

Basically I have something like this :

let objs = [{x: {y: 1, z: 2}, a: 3}, {x: null, a: 4}];
let sortKeys = ['x.y', 'a']; //this is dynamic, can have multiple fields

The user can pass different values for sorting, like xy or just a and sometimes x is null. So when I use the normal _.orderBy(objs, sortKeys, ['desc']) it shows null values first.

How can I do so that the null values appears last?

Answer 1

This solution partitions the array to values that are null or undefined ( unsortable ) via _.isNil() . It then sorts the sortable items, and concats the unsortable to the end:

 const { partition, get, isNil, orderBy } = _; const fn = (arr, key, order) => { const [unsortable, sortable] = partition(arr, o => isNil(get(o, key))); return orderBy(sortable, key, order) .concat(unsortable); } const objs = [{x: {y: 1, z: 2}, a: 3}, {x: {y: 4, z: 2}, a: 3}, {x: null, a: 4}]; const result = fn(objs, 'x.y', 'desc'); console.log(result); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.2/lodash.min.js"></script> 

Answer 2

Pure ES6 solution would look like this:

 let objs = [{x: {y: 1, z: 2}, a: 3}, {x: null, a: 4}]; objs.sort(({x: x1}, {x: x2}) => { const y1 = x1 === null ? Infinity : x1.y; const y2 = x2 === null ? Infinity : x2.y; return y1 - y2; }); console.log(objs); 

null 's are simply weighted at a maximum possible value and sorted accordingly.