Concat two arrays with filtering

Question

I have two arrays. I need to combine both of them and make a new array which has dayOfWeek 2, 3, 4, 5, 6. Which means priority for the dayOfWeek is in array1. Means need to keep dayOfWeek 3, 4, 5 from array1.

array1 = [
  {dayOfWeek: 2, home1: "01:30"},
  {dayOfWeek: 3, home1: "02:30"},
  {dayOfWeek: 4, home1: "03:30"},
  {dayOfWeek: 5, home1: "04:30"},
]

array2 = [
  {dayOfWeek: 3, home1: "05:30"},
  {dayOfWeek: 4, home1: "06:30"},
  {dayOfWeek: 5, home1: "07:30"},
  {dayOfWeek: 6, home1: "08:30"},
]

Output should be

finalArray = [
  {dayOfWeek: 2, home1: "01:30"},
  {dayOfWeek: 3, home1: "02:30"},
  {dayOfWeek: 4, home1: "03:30"},
  {dayOfWeek: 5, home1: "04:30"},
  {dayOfWeek: 6, home1: "08:30"},
]

I tried this but it pushes the dayOfWeek from both the arrays. How can I filter them?

const finalArray = []
array1.map((a) => {
    array2.map((a2) => {
        if (a.dayOfWeek === a2.dayOfWeek) {
          finalArray.push(a)
        }
        if (a.dayOfWeek === a2.dayOfWeek) {
          finalArray.push(a2)
        }
    })
})

Thanks in advance!!!

score 3 · Answer 1 · answered Nov 23 '18 at 10:08

You could also simply filter the second array for the items missing form the first and then concatenate those to the first array without lodash:

const a1 = [ {dayOfWeek: 2, home1: "01:30"}, {dayOfWeek: 3, home1: "02:30"}, {dayOfWeek: 4, home1: "03:30"}, {dayOfWeek: 5, home1: "04:30"}, ]
const a2 = [ {dayOfWeek: 3, home1: "05:30"}, {dayOfWeek: 4, home1: "06:30"}, {dayOfWeek: 5, home1: "07:30"}, {dayOfWeek: 6, home1: "08:30"}, ]

const r = a1.concat(a2.filter(x => !a1.some(y => y.dayOfWeek == x.dayOfWeek)))

console.log(r)

This is done via Array.concat, Array.filter and Array.some

score 2 · Answer 2 · answered Nov 23 '18 at 08:45

You can also use Set and Array.filter

let array1 = [
  {dayOfWeek: 2, home1: "01:30"},
  {dayOfWeek: 3, home1: "02:30"},
  {dayOfWeek: 4, home1: "03:30"},
  {dayOfWeek: 5, home1: "04:30"},
]

let array2 = [
  {dayOfWeek: 3, home1: "05:30"},
  {dayOfWeek: 4, home1: "06:30"},
  {dayOfWeek: 5, home1: "07:30"},
  {dayOfWeek: 6, home1: "08:30"},
]

let s = new Set()
console.log([...array1, ...array2].filter(d => {
    let avail = s.has(d.dayOfWeek)
    !avail && s.add(d.dayOfWeek)
    return !avail
  }
) )

Ori Drori · Accepted Answer · 2018-12-06T09:24:18.393

2

Use lodash's _.unionBy(). The predominant array should be the 1st array passed to the function.

const array1 = [{"dayOfWeek":2,"home1":"01:30"},{"dayOfWeek":3,"home1":"02:30"},{"dayOfWeek":4,"home1":"03:30"},{"dayOfWeek":5,"home1":"04:30"}]
const array2 = [{"dayOfWeek":3,"home1":"05:30"},{"dayOfWeek":4,"home1":"06:30"},{"dayOfWeek":5,"home1":"07:30"},{"dayOfWeek":6,"home1":"08:30"}]

const result = _.unionBy(array1, array2, 'dayOfWeek')

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

If you need to combine several properties to use as the union value, you can use:

_.unionBy(array1, array2, o => `${o.id}-${o.dayOfWeek}`)

edited Dec 06 '18 at 09:24

answered Nov 23 '18 at 11:31

Ori Drori

183,571
29
224
209

Can I use two fields for the `_.unionBy` . I need to union by `dayOfWeek` and `id`? – Profer Dec 06 '18 at 09:17
See addition to the answer. – Ori Drori Dec 06 '18 at 09:24

score 1 · Answer 4 · answered Nov 23 '18 at 08:23

1

you can use array concatenation method and after that do filter.

var c = array1.concat(array2);

answered Nov 23 '18 at 08:23

shaan26

37
7

sorry but I don't want to concat. BTW Thank you for the answer. – Profer Nov 23 '18 at 10:34

score 1 · Answer 5 · answered Nov 23 '18 at 08:23

1

Profer. You could use Map object to get unique elements

const array1 = [
  {dayOfWeek: 2, home1: "01:30"},
  {dayOfWeek: 3, home1: "02:30"},
  {dayOfWeek: 4, home1: "03:30"},
  {dayOfWeek: 5, home1: "04:30"},
];

const array2 = [
  {dayOfWeek: 3, home1: "05:30"},
  {dayOfWeek: 4, home1: "06:30"},
  {dayOfWeek: 5, home1: "07:30"},
  {dayOfWeek: 6, home1: "08:30"},
];

function getFinalArray(array, uniqueProperty) {
  return array
    .filter(value => value)
    .reduce(
      (arrayMap, item) => {
        return arrayMap.set(item[uniqueProperty], item)
      }, new Map()
    );
}

const result = Array.from(
  getFinalArray([...array2, ...array1], 'dayOfWeek').values()
);

answered Nov 23 '18 at 08:23

Evgeniy Boytsov

214
2
8

If you don't want the order to get mangled you could do: `.reduce( (arrayMap, item) => !arrayMap.get(item[uniqueProperty]) ? arrayMap.set(item[uniqueProperty], item) : arrayMap, new Map(),` pass in the arrays as [...array1,...array2]` – HMR Nov 23 '18 at 08:50
Thanks for the addition. it could be nice to **do check** this way `arrayMap.has(item[uniqueProperty])` instead – Evgeniy Boytsov Nov 23 '18 at 09:02

cнŝdk · Answer 6 · 2018-11-23T08:40:28.747

You can use a combination of Array#slice(), Array#forEach() and Array#some() methods:

Use .slice(0) to get all elements of array1 in finalArray.
Then use .forEach() to iterate over array2 and get all elements that doesn't exist in finalArray.
Use .some() to check if the iterated element (dayOfWeek) exist.

This is how should be your code:

var finalArray = array1.slice(0);
array2.forEach(function(a){
      if(!finalArray.some(e => e.dayOfWeek == a.dayOfWeek))
          finalArray.push(a);
});

Demo:

let array1 = [
  {dayOfWeek: 2, home1: "01:30"},
  {dayOfWeek: 3, home1: "02:30"},
  {dayOfWeek: 4, home1: "03:30"},
  {dayOfWeek: 5, home1: "04:30"},
];

let array2 = [
  {dayOfWeek: 3, home1: "05:30"},
  {dayOfWeek: 4, home1: "06:30"},
  {dayOfWeek: 5, home1: "07:30"},
  {dayOfWeek: 6, home1: "08:30"},
];

var finalArray = array1.slice(0);
array2.forEach(function(a){
      if(!finalArray.some(e => e.dayOfWeek == a.dayOfWeek))
          finalArray.push(a);
});

console.log(finalArray);

Concat two arrays with filtering

6 Answers6