Develop Reference

Group array of objects by multiple nested values

I have an array of objects which presents tasks. These tasks are categorized (primary / secondary category).
let tasks = [
{
id: 1,
name: 'Cleanup desk',
primary_category: {
id: 1,
name: 'Indoor'
},
secondary_category: {
id: 2,
name: 'Surfaces'
}
},
{
id: 2,
name: 'Cleanup office floors',
primary_category: {
id: 1,
name: 'Indoor'
},
secondary_category: {
id: 3,
name: 'Ground'
}
},
{
id: 3,
name: 'Water plants',
primary_category: {
id: 2,
name: 'Outdoor'
},
secondary_category: {
id: 3,
name: 'Irrigation'
}
}
];
I now try to create a categories accordion in my frontend and therefore need to group my array differently. The structure should look like:
1) primary category
> secondary category
> tasks
> secondary category
> tasks
2) primary category
> secondary category
> tasks
Therefore I'm trying to achieve a structure similar to this:
let tasks_categorized = [
{
id: 1,
name: 'Indoor',
secondary_categories: [
{
id: 2,
name: 'Surfaces',
tasks: [
{
id: 1,
name: 'Cleanup desk'
}
]
},
{
id: 3,
name: 'Ground',
tasks: [
{
id: 2,
name: 'Cleanup office floors'
}
]
}
]
},
{
id: 2,
name: 'Outdoor',
secondary_categories: [
{
id: 3,
name: 'Irrigation',
tasks: [
{
id: 3,
name: 'Water plants'
}
]
}
]
}
];
I tried using groupBy by lodash but this does not allow grouping by multiple nested key-value pairs. Does anybody know an approach to solve this?
Thank you in advance!

The following provided approach is going to achieve the expected result within a single reduce cycle without any further nested loops.
It does so by implementing a reducer function which creates and/or aggregates at time a prioritized category task while iterating another task array. But most importantly it keeps track of a task item's related primary and secondary categories via a Map based lookup. This lookup reference together with a result array are properties of this function's return value which has to be partly provided as the reduce method's initial value as follows ... { result: [] }.
function createAndAggregatePrioritizedCategoryTask(
{ lookup = new Map, result }, item
) {
const { primary_category, secondary_category, ...taskRest } = item;
const { id: primaryId, name: primaryName } = primary_category;
const { id: secondaryId, name: secondaryName } = secondary_category;
const primaryKey = [primaryId, primaryName].join('###');
const secondaryKey = [primaryKey, secondaryId, secondaryName].join('###');
let primaryCategory = lookup.get(primaryKey);
if (!primaryCategory) {
// create new primary category item.
primaryCategory = {
id: primaryId,
name: primaryName,
secondary_categories: [],
};
// store newly created primary category reference in `lookup`.
lookup.set(primaryKey, primaryCategory);
// push newly created primary category reference to `result`.
result.push(primaryCategory);
}
let secondaryCategory = lookup.get(secondaryKey);
if (!secondaryCategory) {
// create new secondary category item.
secondaryCategory = {
id: secondaryId,
name: secondaryName,
tasks: [],
};
// store newly created secondary category reference in `lookup`.
lookup.set(secondaryKey, secondaryCategory);
// push newly created secondary category reference into the
// `secondary_categories` array of its related primary category.
primaryCategory
.secondary_categories
.push(secondaryCategory);
}
// push the currently processed task-item's rest-data as
// item into the related secondary category's `task` array.
secondaryCategory
.tasks
.push(taskRest);
return { lookup, result };
}
let tasks = [{
id: 1,
name: 'Cleanup desk',
primary_category: { id: 1, name: 'Indoor' },
secondary_category: { id: 2, name: 'Surfaces' },
}, {
id: 2,
name: 'Cleanup office floors',
primary_category: { id: 1, name: 'Indoor' },
secondary_category: { id: 3, name: 'Ground' },
}, {
id: 3,
name: 'Water plants',
primary_category: { id: 2, name: 'Outdoor' },
secondary_category: { id: 3, name: 'Irrigation' },
}];
const { result: tasks_categorized } = tasks
.reduce(createAndAggregatePrioritizedCategoryTask, { result: [] });
console.log({ tasks_categorized });
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You could take a dynamic approach with an array of arrays with functions and keys for the nested arrays.
const
tasks = [{ id: 1, name: 'Cleanup desk', primary_category: { id: 1, name: 'Indoor' }, secondary_category: { id: 2, name: 'Surfaces' } }, { id: 2, name: 'Cleanup office floors', primary_category: { id: 1, name: 'Indoor' }, secondary_category: { id: 3, name: 'Ground' } }, { id: 3, name: 'Water plants', primary_category: { id: 2, name: 'Outdoor' }, secondary_category: { id: 3, name: 'Irrigation' } }],
groups = [
[o => o, 'primary category'],
[o => o.primary_category, 'secondary category'],
[o => o.secondary_category, 'tasks']
],
result = tasks.reduce((r, o) => {
groups.reduce((parent, [fn, children]) => {
const { id, name } = fn(o);
let item = (parent[children] ??= []).find(q => q.id === id)
if (!item) parent[children].push(item = { id, name });
return item;
}, r);
return r;
}, {})[groups[0][1]];
console.log(result);
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How do I check that the correct objects are being returned via a function (expect function returns [Function Anonymous])?

I have a function:
const sort =
(pets,attribute) =>
_(pets)
.filter(pets=> _.get(pets, attribute) !== null)
.groupBy(attribute)
.value()
Some data:
const pets= [{
id: 1,
name: 'snowy',
},
{
id: 2,
name: 'quacky',
},
{
id: 3,
name: 'snowy',
age: 5,
},
{
id: null,
name: null,
age: null
}
]
const attribute = 'name'
I am currently trying to write some Jest unit tests for this, that tests if the function returns the correct resultant object after being sorted based off an attribute.
The result of:
sort(pets,attribute) is something like this:
{
snowy: [ { id: 1, name: 'snowy' }, { id: 3, name: 'snowy', age: 5} ],
quacky: [ { id: 2, name: 'quacky' } ]
}
Is there a way I can do a expect to match the two objects snowy and quacky here?
The thing I want to test for is that the objects are being correctly grouped by the key.
I've tried using something like
const res = sort(users,key)
expect(res).toEqual(
expect.arrayContaining([
expect.objectContaining({'snowy' : [ { id: 1, name: 'snowy' }, { id: 3, name: 'snowy', age: 5 } ]},
expect.objectContaining({'quacky' : [ { id: 2, name: 'quacky' } ]}))
])
)
which doesn't seem to work, the received output seems to output:
Expected: ArrayContaining [ObjectContaining {"snowy": [{"id": 1, "name": "snowy"}, {"age": 5, "id": 3, "name": "snowy"}]}]
Received: [Function anonymous]
I am unsure what the best method to test this kind of function is either so advice on that would be appreciated.

If this is what your arrangeBy() returns:
{
snowy: [ { id: 1, name: 'snowy' }, { id: 3, name: 'snowy', age: 5} ],
quacky: [ { id: 2, name: 'quacky' } ]
}
Then you can just do:
const expected = {
snowy: [ { id: 1, name: 'snowy' }, { id: 3, name: 'snowy', age: 5} ],
quacky: [ { id: 2, name: 'quacky' } ]
}
const res = arrangeBy(users,key)
expect(res).toEqual(expected)
But looking at your Error message I guess you have something else mixed up. In the beginning you listed the implementation of a sort function which seems to not be used in the test. Where is arrangeBy coming from now.
Please provide more code examples.

Adding new values to an array

I want to add new values on my array in javascript. The array is like that:
[
0: { Id: 0,
Name: "First",
Time: "2020-06-08T11:12:03.003" },
1: { Id: 1,
Name: "Second",
Time: "2020-06-08T11:12:03.003" }
]
This is a simple array, my array is bigger and more values. I want to add new values like that:
[
0: { Id: 0,
Name: "First",
Time: "2020-06-08T11:12:03.003",
SecondTime: "2020-06-08T11:12:03.003" },
1: { Id: 1,
Name: "Second",
Time: "2020-06-08T11:12:03.003",
SecondTime: "2020-06-08T11:12:03.003" }
]
I know there are a lot of similar questions but i couldn't find any solution to my problem.

using foreach
const data = [
{ Id: 0,
Name: "First",
Time: "2020-06-08T11:12:03.003" },
{ Id: 1,
Name: "Second",
Time: "2020-06-08T11:12:03.003" }
]
data.forEach(i=> i.SecondTime = i.Time);
console.log(data)
Using reduce:
const data = [
{ Id: 0,
Name: "First",
Time: "2020-06-08T11:12:03.003" },
{ Id: 1,
Name: "Second",
Time: "2020-06-08T11:12:03.003" }
]
var res = data.reduce((acc, elem)=>{
elem.Secondtime = elem.Time;
return acc = [...acc, elem];
},[]);
console.log(res)

let blah = {
0: { Id: 0,
Name: "First",
Time: "2020-06-08T11:12:03.003"},
1: { Id: 1,
Name: "Second",
Time: "2020-06-08T11:12:03.003" }
};
Object.keys(blah).forEach((ele)=>{
blah[ele].SecondTime = "2020-06-08T11:12:03.003"
});
console.log(blah);
Hope this helps

In an alternative to foreach and reduce answers, you can use map. Has you can see here, for changing data, the map has a little better performance over foreach loops or reduce fucntions.
Follows a full working example:
const originalArray = [
{ 0: { Id: 0,
Name: "First",
Time: "2020-06-08T11:12:03.003" }},
{ 1: { Id: 1,
Name: "Second",
Time: "2020-06-08T11:12:03.003" }}
]
const transformedArray = originalArray.map((element, index) => {
element[index].SecondTime = new Date();
return element;
});
console.log(transformedArray);

JavaScript - Is there a simple way to get the values for every occurrence of a specific key in nested JSON

I have a JSON structure similar to this:
[
{
cells: [
{ id: "1", cellType: 3, widget: { id: 1, description: "myDesc"} },
{ id: "2", cellType: 4, widget: { id: 2, description: "myDesc2"} }
]
},
{
cells: [
{ id: "3", cellType: 5, widget: { id: 3, description: "myDesc3"} }
]
},
...
]
How do I get the value of every widget into a separate array using EcmaScript (or anything that's available in Angular 2+), and without using a library (including JQuery)? I need a final array like this:
[
{
id: 1,
description: "myDesc"
},
{
id: 2,
description: "myDesc2"
},
...
]
Update
(and thanks to #Felix Kling for the 1st part) - I found I can get all of the widgets with this:
JSON.parse(json)[0].forEach( c => c.cells.forEach( c2 => console.log(c2.widget)));

You can use .map() with .reduce()
let input = [
{
cells: [
{ id: "1", cellType: 3, widget: { id: 1, description: "myDesc"} },
{ id: "1", cellType: 4, widget: { id: 2, description: "myDesc2"} }
]
},
{
cells: [
{ id: "3", cellType: 5, widget: { id: 3, description: "myDesc3"} }
]
},
];
let result = input.reduce((result, current) => {
return result.concat(current.cells.map(x => x.widget));
}, [])
console.log(result);

You can use .map() and .concat() to get the desired result:
let data = [{
cells: [
{ id: "1", cellType: 3, widget: { id: 1, description: "myDesc"} },
{ id: "1", cellType: 4, widget: { id: 2, description: "myDesc2"} }
]}, {
cells: [
{ id: "3", cellType: 5, widget: { id: 3, description: "myDesc3"} }
]
}];
let result = [].concat(...data.map(({cells}) => cells.map(({widget}) => widget)));
console.log(result);
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Reorder array of objects based on attribute

I have an array of objects, each with an 'id' and a 'name'. I'm retrieving an 'id' from the server and need to reorder the array starting from this id.
Example code:
var myList = [
{
id: 0,
name: 'Joe'
},
{
id: 1,
name: 'Sally'
},
{
id: 2,
name: 'Chris'
},
{
id: 3,
name: 'Tiffany'
},
{
id: 4,
name: 'Kerry'
}
];
Given an 'id' of 2, how can I reorder the array so my output is as follows:
var newList = [
{
id: 2,
name: 'Chris'
},
{
id: 3,
name: 'Tiffany'
},
{
id: 4,
name: 'Kerry'
},
{
id: 0,
name: 'Joe'
},
{
id: 1,
name: 'Sally'
}
];

Try this:
function orderList(list, id){
return list.slice(id).concat(list.slice(0,id));
}
Link to demo

You could slice the array at given index and return a new array using spread syntax.
const myList = [{id:0,name:'Joe'},{id:1,name:'Sally'},{id:2,name:'Chris'},{id:3,name:'Tiffany'},{id:4,name:'Kerry'}];
const slice = (arr, num) => [...arr.slice(num), ...arr.slice(0, num)];
console.log(slice(myList, 2));

myList.sort(function(a,b){
return a.id>2===b.id>2?a.id-b.id:b.id-a.id;
});
newList=myList;
http://jsbin.com/kenobunali/edit?console

You could splice the wanted part and use splice to insert it at the end of the array.
var myList = [{ id: 0, name: 'Joe' }, { id: 1, name: 'Sally' }, { id: 2, name: 'Chris' }, { id: 3, name: 'Tiffany' }, { id: 4, name: 'Kerry' }],
id = 2;
myList.splice(myList.length, 0, myList.splice(0, myList.findIndex(o => o.id === id)));
console.log(myList);

using es6 spread syntax
var myList = [{ id: 0, name: 'Joe' }, { id: 1, name: 'Sally' }, { id: 2, name: 'Chris' }, { id: 3, name: 'Tiffany' }, { id: 4, name: 'Kerry' }],
id = 2;
var index = myList.findIndex(o => o.id == id);
var arr = myList.splice(0, index);
var result = [...myList, ...arr];
console.log(result);