groupBy first, then sort array based on name with lodash?

Question

I have some json in the form of:

data = { 
    "1": {"name": "eve", "type": "sergeant", "age": 22},
    "2": {"name": "bob", "type": "sergeant", "age": 33},
    "3": {"name": "bats", "type": "private", "age": 90},
    "4": {"name": "carol", "type": "captain", "age": 50},
    "5": {"name": "noogle", "type": "sergeant", "age": 34},
    "6": {"name": "good", "type": "sergeant", "age": 47},
    "7": {"name": "alice", "type": "private", "age": 34}
}

How can I groupBy their type , and then within each type, they are sorted by their name in ascending order?

I tried to do it with:

let grouped = _.groupBy(Object.keys(data), function(id) {
    return data[id].type;
});

Which will give me something like:

{
    "sergeant": ["1", "2", "5", "6"],
    "private": ["3", "7"],
    "captain": ["4"]
}

But when I try to sortBy it gives me the same object as above:

_.map(Object.keys(grouped), function(type_name) {
    grouped[type_name] = _.sortedBy(grouped[type_name], function(id) {
        return data[id].name;
    });
});

How can I sort the array after I've grouped the objects together? Is there a way I can cleanly chain groupBy and sortBy together instead of splitting logic like I have above?

Answer 1

You can use the _.mapValues method to sort each group after you've grouped them up by using _.groupBy . Just take each value and return the sorted version of it in your _.mapValues callback function.

Example:

 data = { "1": {"name": "eve", "type": "sergeant", "age": 22}, "2": {"name": "bob", "type": "sergeant", "age": 33}, "3": {"name": "bats", "type": "private", "age": 90}, "4": {"name": "carol", "type": "captain", "age": 50}, "5": {"name": "noogle", "type": "sergeant", "age": 34}, "6": {"name": "good", "type": "sergeant", "age": 47}, "7": {"name": "alice", "type": "private", "age": 34} } console.log(_.mapValues(_.groupBy(data, "type"), v => _.sortBy(v, "name"))) 

 <script src="https://cdn.jsdelivr.net/npm/lodash@4.17.10/lodash.min.js"></script> 

Or, if you just want grouped and sorted keys, or grouped and sorted key/values, you can use the same approach, although its not quite as easy on the eyes:

 data = { "1": {"name": "eve", "type": "sergeant", "age": 22}, "2": {"name": "bob", "type": "sergeant", "age": 33}, "3": {"name": "bats", "type": "private", "age": 90}, "4": {"name": "carol", "type": "captain", "age": 50}, "5": {"name": "noogle", "type": "sergeant", "age": 34}, "6": {"name": "good", "type": "sergeant", "age": 47}, "7": {"name": "alice", "type": "private", "age": 34} } // If all you want are grouped and sorted keys: console.log(_.mapValues(_.groupBy(_.keys(data), k => data[k].type), v => _.sortBy(v, i => data[i].name))) // Or for grouped and sorted keys and values: console.log(_.mapValues(_.groupBy(_.keys(data), k => data[k].type), v => _.sortBy(v, i => data[i].name).map(k => ({[k]: data[k]})))) 

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