Increment property in array of objects, conditionally

Question

I am incrementing the value on rank by one till the name property changes, I am using the page and rank properties to determine when that happens.

But I would also like to increment it once when the type is not equal to none and resume when it does again.

I almost have it with this, but I seem to be one step behind, as when the type returns to none still not incrementing.

const data = [
  { name: 'car', rank: 1, page: 1, type: 'another' },
  { name: 'car', rank: 2, page: 1, type: 'none' },
  { name: 'car', rank: 1, page: 2, type: 'none' },
  { name: 'car', rank: 2, page: 2, type: 'none' },
  { name: 'bike', rank: 1, page: 1, type: 'none' },
  { name: 'bike', rank: 2, page: 1, type: 'none' },
  { name: 'bike', rank: 1, page: 2, type: 'something_else' },
  { name: 'bike', rank: 2, page: 2, type: 'something_else' },
  { name: 'bike', rank: 1, page: 3, type: 'something_else' },
  { name: 'bike', rank: 2, page: 3, type: 'none' }, 
  { name: 'moto', rank: 1, page: 1, type: 'not_none' },
  { name: 'moto', rank: 2, page: 1, type: 'not_none' },
  { name: 'moto', rank: 1, page: 2, type: 'none' },
  { name: 'moto', rank: 2, page: 2, type: 'none' },
  { name: 'bus', rank: 1, page: 1, type: 'none' },
  { name: 'bus', rank: 2, page: 1, type: 'none' },
  { name: 'bus', rank: 1, page: 2, type: 'none' },
]

let counter = 1

const results = data.reduce((acc, obj) => {

  if (obj.page === 1 && obj.rank === 1) 
    counter = 1

  obj.rank = obj.type === 'none' ? counter++ : counter

  acc.push(obj)
  return acc
}, [])

console.log(results)

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Desired output

[
  { name: 'car', rank: 1, page: 1, type: 'other' },
  { name: 'car', rank: 2, page: 1, type: 'none' },
  { name: 'car', rank: 3, page: 2, type: 'none' },
  { name: 'car', rank: 4, page: 2, type: 'none' },

  { name: 'bike', rank: 1, page: 1, type: 'none' },
  { name: 'bike', rank: 2, page: 1, type: 'none' },
  { name: 'bike', rank: 3, page: 2, type: 'something_else' },
  { name: 'bike', rank: 3, page: 2, type: 'something_else' },
  { name: 'bike', rank: 3, page: 3, type: 'something_else' },
  { name: 'bike', rank: 4, page: 3, type: 'none' },

  { name: 'moto', rank: 1, page: 1, type: 'not_none' },
  { name: 'moto', rank: 1, page: 1, type: 'not_none' },
  { name: 'moto', rank: 2, page: 2, type: 'none' },
  { name: 'moto', rank: 3, page: 2, type: 'none' },

  { name: 'bus', rank: 1, page: 1, type: 'none' },
  { name: 'bus', rank: 2, page: 1, type: 'none' },
  { name: 'bus', rank: 3, page: 2, type: 'none' }
]

trincot · Accepted Answer · 2021-03-23 22:15:41Z

2

So the rank should increase when either the current or the previous type is "none". You can access the previous one via the third and fourth argument to reduce.

const data = [
  { name: 'car', rank: 1, page: 1, type: 'none' },
  { name: 'car', rank: 2, page: 1, type: 'none' },
  { name: 'car', rank: 1, page: 2, type: 'none' },
  { name: 'car', rank: 2, page: 2, type: 'none' },
  { name: 'bike', rank: 1, page: 1, type: 'none' },
  { name: 'bike', rank: 2, page: 1, type: 'none' },
  { name: 'bike', rank: 1, page: 2, type: 'something_else' },
  { name: 'bike', rank: 2, page: 2, type: 'something_else' },
  { name: 'bike', rank: 1, page: 3, type: 'something_else' },
  { name: 'bike', rank: 2, page: 3, type: 'none' }, 
  { name: 'moto', rank: 1, page: 1, type: 'not_none' },
  { name: 'moto', rank: 2, page: 1, type: 'not_none' },
  { name: 'moto', rank: 1, page: 2, type: 'none' },
  { name: 'moto', rank: 2, page: 2, type: 'none' },
  { name: 'bus', rank: 1, page: 1, type: 'none' },
  { name: 'bus', rank: 2, page: 1, type: 'none' },
  { name: 'bus', rank: 1, page: 2, type: 'none' },
]

let counter = 1

const results = data.reduce((acc, obj, i, data) => {

  if (obj.page === 1 && obj.rank === 1) 
    counter = 0;

  obj.rank = [obj.type, data[i-1]?.type].includes('none') || !i ? ++counter : counter;

  acc.push(obj)
  return acc
}, [])

console.log(results)

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edited Mar 23, 2021 at 22:15

answered Mar 23, 2021 at 21:46

trincot

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3 Comments

Álvaro Over a year ago

Nice, I forgot about the optional chaining ?.

Álvaro Over a year ago

There is one problem with this answer, if the first object type is also not none, its rank would be 0

trincot Over a year ago

True, I added || !i to deal with this.

loop · Accepted Answer · 2021-03-23 21:44:58Z

1

const data = [
  { name: 'car', rank: 1, page: 1, type: 'none' },
  { name: 'car', rank: 2, page: 1, type: 'none' },
  { name: 'car', rank: 1, page: 2, type: 'none' },
  { name: 'car', rank: 2, page: 2, type: 'none' },
  { name: 'bike', rank: 1, page: 1, type: 'none' },
  { name: 'bike', rank: 2, page: 1, type: 'none' },
  { name: 'bike', rank: 1, page: 2, type: 'something_else' },
  { name: 'bike', rank: 2, page: 2, type: 'something_else' },
  { name: 'bike', rank: 1, page: 3, type: 'something_else' },
  { name: 'bike', rank: 2, page: 3, type: 'none' }, 
  { name: 'moto', rank: 1, page: 1, type: 'not_none' },
  { name: 'moto', rank: 2, page: 1, type: 'not_none' },
  { name: 'moto', rank: 1, page: 2, type: 'none' },
  { name: 'moto', rank: 2, page: 2, type: 'none' },
  { name: 'bus', rank: 1, page: 1, type: 'none' },
  { name: 'bus', rank: 2, page: 1, type: 'none' },
  { name: 'bus', rank: 1, page: 2, type: 'none' },
]

let counter = 1
let skip = false

const results = data.reduce((acc, obj) => {

  if (obj.page === 1 && obj.rank === 1) {
    counter = 0
    skip = false
  }
  if (obj.type !== 'none') {
    if (!skip) {
      skip = true
      counter++
    }
  } else {
    skip = false;
    counter++
  }
  
  obj.rank = counter

  acc.push(obj)
  return acc
}, [])

console.log(results)

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The condition could maybe be condensed to:

  if (obj.type === 'none' || !skip ) {
    skip = (obj.type !== 'none')
    counter++;
  }

edited Mar 23, 2021 at 21:44

answered Mar 23, 2021 at 21:37

loop

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3 Comments

Álvaro Over a year ago

Thanks for your answer, I actually managed to do it by using the index and array other arguments in the reduce method to go back in the array and check its type

loop Over a year ago

Right. You need some kind of history information there. "Skip" was my choice.

Álvaro Over a year ago

I did this: if (obj.page === 1 && obj.rank === 1) counter = 0 if (obj.type === 'none' || index === 0) counter++ else if (index > 0 && array[index -1].type !== obj.type ) counter++

Álvaro · Accepted Answer · 2021-03-23 22:19:44Z

I ended up doing this, it addresses the fact that if the first object type is also not none it would still add rank 1, thanks to everyone for the responses and to trincot for remind me of the optional chaining

const data = [ { name: 'car', rank: 1, page: 1, type: 'other' }, { name: 'car', rank: 2, page: 1, type: 'none' }, { name: 'car', rank: 1, page: 2, type: 'none' }, { name: 'car', rank: 2, page: 2, type: 'none' }, { name: 'bike', rank: 1, page: 1, type: 'none' }, { name: 'bike', rank: 2, page: 1, type: 'none' }, { name: 'bike', rank: 1, page: 2, type: 'somethingelse' }, { name: 'bike', rank: 2, page: 2, type: 'somethingelse' }, { name: 'bike', rank: 1, page: 3, type: 'somethingelse' }, { name: 'bike', rank: 2, page: 3, type: 'none' }, { name: 'moto', rank: 1, page: 1, type: 'not_none' }, { name: 'moto', rank: 2, page: 1, type: 'not_none' }, { name: 'moto', rank: 1, page: 2, type: 'none' }, { name: 'moto', rank: 2, page: 2, type: 'none' }, { name: 'bus', rank: 1, page: 1, type: 'none' }, { name: 'bus', rank: 2, page: 1, type: 'none' }, { name: 'bus', rank: 1, page: 2, type: 'none' }, ]

let counter = 0

const relative = data.reduce((acc, obj, index, array) => {

  if (obj.page === 1 && obj.rank === 1) counter = 0
  if (obj.type === 'none' || array[index -1]?.type !== obj.type) counter++
  
  obj.rank = counter
  acc.push(obj)
  return acc
}, [])

console.log(relative)

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