Retrieve a flattened array of values taken from an object array that exists within a top-level object of which I am given an array

Question

Please feel free to modify title, it was rather hard for me to explain and thus search.

var booking = [
 {
    x: "1",
    y: "2",
    days: [
       {
           hours: 8
       },     
    ]
 },
 {...}
]

var hoursBooked = [8, 2, 4, 8, 2, 8, 3, 4]; // this is what I want

So I have an array of 'Booking' objects. Each Booking can have a number of days in an array of 'Day' objects. In the 'Day' object lies an 'Hours' property.

All I want to do - is loop through the bookings array and output a flattened array of 'Hours' values (so I can visualise in a graph).

I am sure there's a nice functional or otherwise clean approach to doing this rather than using a sequence of 'for' loops.

Anyone?

at least, you could add a classical approach to the question. — Nina Scholz, May 24 '17 at 10:51
Do you mean in terms of what I have already attempted? The solution I had used was nested for loops, but I specified in the question I wasn't looking for that answer and instead something more functional — aspirant_sensei, May 24 '17 at 10:58

score 2 · Answer 1 · answered May 24 '17 at 10:54

2

Lodash 4x

var booking = [
 {
    x: "1",
    y: "2",
    days: [
       {
           hours: 8
       },     
    ]
 },
 {
    x: "1",
    y: "2",
    days: [
       {
           hours: 3
       },  
       {
           hours: 5
       }   
    ]
 }
];


_(booking).map('days').flatten().map('hours').value();

Will print

[8, 3, 5]

answered May 24 '17 at 10:54

ninhjs.dev

7,203
1
49
35

this is precisely what i was looking for - is there a non lo-dash/underscore variant you could give? – aspirant_sensei May 24 '17 at 10:56

score 1 · Accepted Answer · answered May 24 '17 at 10:59

1

You could reduce booking with the values of the days arrays.

var booking = [{ x: "1", y: "2", days: [{ hours: 8 }, { hours: 4 }, ] }, { x: "3", y: "4", days: [{ hours: 1 }, { hours: 3 }, ] }, { x: "3", y: "4", days: [] }],
    hoursBooked = booking.reduce((r, a) => r.concat((a.days || []).map(d => d.hours)), []);

console.log(hoursBooked);

answered May 24 '17 at 10:59

Nina Scholz

376,160
25
347
392

Perfect, vanilla javascript implementation and gets the job done really nicely. Thanks – aspirant_sensei May 24 '17 at 11:03

score 0 · Answer 3 · answered May 24 '17 at 10:52

0

var booking = [
 {
    x: "1",
    y: "2",
    days: [
       {
           hours: 8
       },     
       {
           hours: 2
       }
    ]
 },
 {
    x: "1",
    y: "2",
    days: [
       {
           hours: 4
       },     
    ]
 }
]
var hoursBooked = []
booking.forEach(b=>b.days.forEach(d=>hoursBooked.push(d.hours)))
console.log(hoursBooked)

answered May 24 '17 at 10:52

Michał Sałaciński

2,256
1
11
10

This is the solution I had - basically nested for loop, I was just wondering if there was a handy functional approach. – aspirant_sensei May 24 '17 at 10:55

Retrieve a flattened array of values taken from an object array that exists within a top-level object of which I am given an array

3 Answers3