Angular Filter and Merge Array of Objects

Question

I have:

arrayBefore

arrayBefore = [{name:'n1', items: [i1]}, {name:'n2', items: [i2]}, {name:'n1', items: [i3]}]

I want to create a function:

myFunction

myFunction(arrayBefore)

So it will produce:

arrayAfter

arrayAfter = [{name:'n1', items: [i1, i3]}, {name:'n2', items: [i2]}]

I have tried to implement myFunction using map() and filter(), but I can't get it working correctly. I would show some code I tried if I had the idea I was getting close, unfortunatly this is not the case. Any help would be greatly appreciated!

score 1 · Answer 1 · answered Dec 19 '19 at 15:51

1

This looks like the groupBy operation. It's not doable by only map and filter. You need a reduce. See an example here

answered Dec 19 '19 at 15:51

Tiberiu Maran

1,983
16
23

It seems like the example was indeed the solution. I accepted the answer from @StepUp because it was the first correct one to come in. – Niels Ferguson Dec 20 '19 at 09:16

score 1 · Accepted Answer · answered Dec 19 '19 at 18:07

1

reduce method is what you are looking for:

const result = arr.reduce((a, {name, items})=>{
     a[name] = a[name] || { name, items:[] };
     a[name].items.push(...items)
     return a;
 }, {});

An example:

let arr = [
    { name: 'n1', items: ['i1'] },
    { name: 'n2', items: ['i2'] },
    { name: 'n1', items: ['i3'] }
];

const result = arr.reduce((a, {name, items})=>{
     a[name] = a[name] || { name, items:[] };
     a[name].items.push(...items)
     return a;
 }, {});
 
 console.log(Object.values(result))

answered Dec 19 '19 at 18:07

StepUp

36,391
15
88
148

1

It took me some time to understand what is going on. But it works perfect! – Niels Ferguson Dec 20 '19 at 09:13
@NielsFerguson I am glad to help you!:) – StepUp Dec 20 '19 at 09:14

Angular Filter and Merge Array of Objects

2 Answers2