Sort object by value with lodash

问题

I have an object that looks like this:

var unsorted = {a: 15, b: 1,c: 2, d: 4, e: 3, f: 6, g: 1}

And I am interested in sorted it in descending order with lodash, so the expected result should be:

var sortd = {b: 1, g: 1,c: 2, e: 3, d: 4, f: 6, a: 15}

I have tried using lodash orderBy but it gives an array of just the values sorted.

_.orderBy(tempCount, Number, ['desc'])

//Result
[1,1,2,3,4,6,15]

回答1:

You could build a new object with the sorted key/value pairs.

The actual standard or the order of properties:

sort index like keys first, in order
keep all other keys in insertation order

For a complete control over the order, take an array with the keys an take it as sorted accessor for the values.

var unsorted = { a: 15, b: 1,c: 2, d: 4, e: 3, f: 6, g: 1 },
    sorted = _(unsorted)
        .toPairs()
        .orderBy([1], ['desc'])
        .fromPairs()
        .value()
        
console.log(sorted);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

Descending sort with _.orderBy by using a the last parameter for a specific order, instead of _.sortBy, which only allows to sort ascending.

var unsorted = { a: 15, b: 1,c: 2, d: 4, e: 3, f: 6, g: 1 },
    sorted = _(unsorted)
        .toPairs()
        .orderBy(1, 'desc')
        .fromPairs()
        .value()
        
console.log(sorted);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

回答2:

JavaScript does not guarantee the order of keys in an object, this is why lodash returns you an array, because an object with ordered keys is not guaranteed. See this SO question.

However you can use a Map, which does guarantee the order of the keys.

You can do this with pure JavaScript:

const unsorted = { a: 15, b: 1,c: 2, d: 4, e: 3, f: 6, g: 1 };

const sorted = new Map(Object.entries(unsorted).sort((a, b) => a[1] - b[1]));

for (const [key, val] of sorted) {
  console.log(key, val);
}

You have multiple ways to iterate over the content of the resulting map:

map.values(): get the array of values
map.entries(): get an array of [key, value] pairs
map.keys(): get an array of keys

See the doc about Map.

回答3:

Here you have another approach (without lodash). Basically we create and array of type [[key1, value1], [key2, value2],...] using the Object.entries(unsorted), then sort that array (ascending/descending) comparing the values, to finally construct again the object structure you have originally, first mapping pairs [key, value] to objects {key: value} and then assigning all these objects to a new one using Object.assign().

var unsorted = {a: 15, b: 1,c: 2, d: 4, e: 3, f: 6, g: 1};

let sortedAsc = Object.entries(unsorted)
    .sort(([k1,v1], [k2,v2]) => v1 - v2)
    .map(([x,y]) => ({[x]:y}));
    
let sortedDesc = Object.entries(unsorted)
    .sort(([k1,v1], [k2,v2]) => v2 - v1)
    .map(([x,y]) => ({[x]:y}));

let objSortedAsc = Object.assign({}, ...sortedAsc);
let objSortedDesc = Object.assign({}, ...sortedDesc);

console.log("ASC: ", objSortedAsc, "DESC: ", objSortedDesc);

来源：https://stackoverflow.com/questions/54520890/sort-object-by-value-with-lodash

标签

javascript

arrays

sorting

lodash