Sort order with multiple keys

[luksch]

Hi, I am a in awe of the power of lodash. For my project it has been of invaluable help so far. However, now I am stuck with a problem with which lodash seems to fall a bit short.

Here is the problem:

I have an array of objects with the same properties, say

[{name:"barney", age: 38},
 {name:"fred", age: 40},
 {name:"fred", age: 12}]

I want to sort the array by name in descending order, but age should be in ascending order.

lodash supports multiple sorting keys by the "pluck" syntax, but only can deal with ascending sorting this way. Is there a way that the sortBy function is altered that it also accepts an array of objects that define the property name (key) and the order direction? I would love to do:

mySortedArr = _.sortby(
    unsortedArr, [
        {propertyName:"name", order:"desc"}, 
        {propertyName:"age", order:"asc"}
    ]);

Any chance something like that enters the library?

[jdalton]

Thanks for the encouragement! I'll keep a tab on this to see if it's requested more, but at the moment I don't have plans to expand this to _.sortBy. You can always iterate over the collection from right to left with _.eachRight, _.reduceRight or the other right associative methods.

[joshbowdoin]

+1 - would definitely like this!

Syntax could be similar to angular's orderBy filter: https://docs.angularjs.org/api/ng/filter/orderBy, where you'd simply put a '+' (optional) or '-' in front of the property name to control ascending/descending.

[octref]

@jdalton
Right associative methods doesn't solve the problem.
For example, suppose this is the result of _.sortBy(myArray, ['foo', 'bar'])

[{'foo': 'A', 'bar': 1}, #1
 {'foo': 'A', 'bar': 2}, #2
 {'foo': 'B', 'bar': 1}, #3
 {'foo': 'B', 'bar': 2}] #4

If I do a reverse, or use right associative methods, I can only get 4-3-2-1.
But what if I want to do a sort with 'foo' ascending and 'bar' descending? The result I want is 2-1-4-3 but I can't seem to achieve that in lodash.

As @joshbowdoin suggests, an optional '-' which indicates descending would be a really nice addition.
Like this _.sortBy(myArray, ['foo', '-bar']) for my example above.

BTW, really nice work. It's saved me tons of hours.

[darthsteedious]

+1 - would love a _.sortBy(myArray, ['foo', '-bar']) syntax.

[ghost1face]

+1

[jdalton]

I'd dig a proposed implementation to go along with the +1's.
In 3.0 we're separating _.sortBy out into _.sortByAll to handle multiple properties. This lets use keep _.sortBy simple.

[leefernandes]

+1 for using an order prefix for each sort

[TrejGun]

You always can add _.sortBySome

[rummelsworth]

I'd love to see sortByAll handle optionally-specified per-criterion descending sort order. (Btw, gotta mention it... Like many others, I am in love with the performance and expressiveness of lodash. Thanks for your awesome work.)

Perhaps a signature something like sortByAll(collection, props, order) for usage like _.sortByAll(myArray, ['foo', 'bar'], [false, true]), to borrow from @octref 's example?

Copying & adapting compareMultipleAscending to compareMultiple seems straightforward (to me at least, relatively new to JS and possibly unaware of some pitfalls):

/**
 * @param {Array} order Each truthy element indicates descending sort order for the corresponding criterion.
 */
function compareMultiple(object, other, order) { // diff
    var index = -1,
        objCriteria = object.criteria,
        othCriteria = other.criteria,
        length = objCriteria.length;

    while (++index < length) {
        var result = baseCompareAscending(objCriteria[index], othCriteria[index]);
        if (result) {
            return order[index] ? -result : result; // diff
        }
    }

    return object.index - other.index;
}

What I like about this approach, using an order-indicating array side-by-side with the criteria array, is that it can easily default to all-ascending when left unspecified/empty. It also doesn't restrict the names of properties like the +/- prefix suggestion does.

The thing I couldn't figure out is correctly modifying sortByAll to "carry" order from the argument list through to e.g. return baseSortBy(result, curryRight(compareMultiple)(order)).

I get tripped up determining whether the iteratee-check area needs any changes, and then also around the call to baseFlatten which might, to continue from the example, end up assigning ['foo', 'bar', false, true] to props if I do something dumb. I don't yet grok things well enough to confidently resolve this.

Anyway, it'd be great to have something like this working for sortByAll. Thanks again.

[jdalton]

I'd prefer an options object, maybe dir with a 1 or -1.

[leefernandes]

Allow props array to optionally contain objects with dir as a value?

var users = [
  { 'user': 'barney', 'age': 36 },
  { 'user': 'fred',   'age': 40 },
  { 'user': 'barney', 'age': 26 },
  { 'user': 'fred',   'age': 30 }
];

// default to standard direction
_.sortByAll(myArray, ['user', 'age'])

or

// define direction
_.sortByAll(myArray, [{user: 1}, {age: -1}])

[jdalton]

Crawling keys is not ideal.
It'd be better to have [{ 'key': 'user', 'dir': 1 }, { 'key': 'age', 'dir': -1 }]

[octref]

I think for the sake of consistency, this might be better:

_.sortByAll(myArray, ['user', 'age'])
_.sortByAll(myArray, {user: 1, age: -1})

iteratee / predicate style, what do you think @jdalton ?

[jdalton]

I'll accept a PR for _.sortByAll(myArray, {user: 1, age: -1}).

[octref]

Sounds good. I guess I'll take a stab at that tonight.

[leefernandes]

Is a sort object an issue since property order of objects are not guaranteed in JavaScript?

Could _.sortByAll(myArray, {user: 1, age: -1}) end up sorting "age" first, where the intention is for the first sort to be of "user"?

4.3.3 Object
An object is a member of the type Object. It is an unordered collection of properties...

http://www.ecma-international.org/publications/files/ECMA-ST-ARCH/ECMA-262,%203rd%20edition,%20December%201999.pdf

[octref]

Right. I guess we'd have to type the long
[{ 'key': 'user', 'dir': 1 }, { 'key': 'age', 'dir': -1 }] then :-(.
And I feel 'dir': 'asc' and 'dir': 'desc' looks better, but that's just my opinion.

[leefernandes]

Maybe to streamline ui implementation consider "reverse: bool" instead of "dir: string".

_.sortByAll(myArray, [{key: "user"}, {key: "age", reverse: true}])

$scope.sort = [{key: 'user'}, {key: 'age', reverse: true}]

<ng-repeat="option in sort">
  <caret ng-click="option.reverse = !option.reverse"></caret>
  <label>{{::option.key}}</label>
</ng-repeat>

[jdalton]

Since sorting is ascending by default how about a desc that's either truthy or not.

[leefernandes]

^^ +1 for desc: true/falsey

[octref]

I'm good with desc true/false.
So it'll look like this:

_.sortByAll(users, [
  { 'key': 'user', 'desc': true },
  { 'key': 'age'}, // Default to 'desc': false
  { 'key': 'gender', 'desc': false } // You can also say that explicitly
]);

[jdalton]

Keep in mind it would only be needed when different than the default. So regular keys could be used for the common case.

[NeevShah]

Hello @jdalton.

Is there any way to pass values with keys in _.sortByAll()? Can I pass boolean as a value?

[jdalton]

Is there any way to pass values with keys in _.sortByAll()? Can I pass boolean as a value?

I'm not sure what you're trying to accomplish. There's _.sortByOrder which allows specifying booleans for sort order direction.

[NeevShah]

I'm responsible for upgrading lodash to 3.8 version from 2.4.1. Where I came to this code where I thought I can improve code.
So my use case is I want to sort array of object by two properties with values.

Example:

var arr = [{"name" :  "test' , type : "1",isActive :true},{"name" :  "tea', type : "2" , isActive :false},{"name" :  "tea' , type : "1", isActive :true}]; 

Now I want to sort first with {"type" : "1" } and then {isActive : false}.
In 2.4.1 I was doing like (works fine for me)

_.sortBy(_.sortBy(arr, {"type" : 1}), {"isActive" : false}));

Can I use _.sortByAll here? I was trying

_.sortByAll(arr, {"type" : 1, "isActive" : false});

but this didn't work for me.

[jdalton]

@NeevShah Let's move this to gitter.

[lock]

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