Nested Group by based on string value Angular 6

Question

Let us say I have a string array with values like -

animal
animal.mammal
animal.bird
animal.reptile
animal.mammal.human
animal.mammal.horse
animal.bird.crow
animal.reptile.snake

When I have to display this array, I want to display it like this -

-animal
  -animal.mammal
    -animal.mammal.human
    -animal.mammal.horse
  -animal.bird
    -animal.bird.crow
  -animal.reptile
    -animal.reptile.snake

What should be my approach? I should use group by or filter or what? I am using angular 6 and material UI.

You will have to group, but not sure if angular provides any in-built one. You can create a custom one though — Rajesh Dixit
– Rajesh Dixit, Commented Jan 24, 2019 at 9:30

Julien METRAL · Accepted Answer · 2019-01-24 10:12:15Z

I have a begin of what you need :

const groups = arr => {
    const res = [];
    arr.forEach(v => {
        let current = res
        const splits = v.split('.');
        splits.forEach(s => {
            if (current[s] === undefined) {
                current[s] = [];
            }
            current = current[s];
        });
        current.push(v);
    }
    return res;

 groups(yourArrayHere);

input :

const arr = ['animal', 'animal.mammal', 'animal.mammal.human'];

output :

[
   'animal': [
       0: 'animal',
       'animal.mammal': [
           0: 'animal.mammal.human'
       ]
   ]
]

Edit :

You can also use reduce statement wich works pretty well too :)

const groups = arr => {
    return arr.reduce((acc, v) => {
       let current = acc
        v.split('.').forEach(s => {
            if (current[s] === undefined) {
                current[s] = [];
            }
            current = current[s];
        });
        current.push(v);
        return acc;
    }, []);
};

groups(theArray);

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