multidimensional default array

Question

I've got two multidimensional arrays:

const defaultData = [
  ["ad", 0],
  ["ae", 0],
  ["af", 0]
]

const data = [
  ["az", 20],
  ["ad", 50]
]

The desired result is:

const expected = [
  ["ad", 50],
  ["ae", 0],
  ["af", 0]
]

Here az is ignored because its not valid because its not in the defaultData. ad is valid and therefore the 0 is overwritten with the value of 50.

How would I best produce this result. Thanks?

Please assume neither array is sorted. The expected result need not be sorted either.

Either vanilla JS or Lodash is fine.

Ori Drori · Accepted Answer · 2019-04-25 14:52:44Z

2

Convert the data to an object (dataByKey) with _.fromPairs(). Map the defaultData, and check if the "key" (index 0) exists in dataByKey. If it is, create a new array with the value from dataByKey. If not return the original array.

const defaultData = [
  ["ad", 0],
  ["ae", 0],
  ["af", 0]
]

const data = [
  ["az", 20],
  ["ad", 50]
]

const dataByKey = _.fromPairs(data)

const result = defaultData.map(o => o[0] in dataByKey ? [o[0], dataByKey[o[0]]] : o)

console.log(result)

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

edited Apr 25, 2019 at 14:52

answered Apr 25, 2019 at 14:00

Ori Drori

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Comments

Andy · Accepted Answer · 2019-04-25 14:02:32Z

1

Use map to iterate over the defaultData, and find to match each iterated array against data:

const defaultData = [['ad', 0],['ae', 0],['af', 0]];
const data = [['az', 20],['ad', 50]];

const expected = defaultData.map(arr => {

  // Destructure the first element from `arr`
  // and assign it to `code`
  const [ code ] = arr;

  // `find` the array in `data` where the first element
  // matches `code`
  const found = data.find(el => el[0] === code);

  // If `found` is undefined return the whole array
  // otherwise return a new array with the code and the value
  // from the found array
  return found ? [code, found[1]] : arr;
});

console.log(expected);

answered Apr 25, 2019 at 14:02

Andy

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Comments

Nenad Vracar · Accepted Answer · 2019-04-25 13:48:00Z

1

You could first create one object from data and then use map method on defaultData to create new array and get value from data by key.

const defaultData = [
  ["ad", 0],
  ["ae", 0],
  ["af", 0]
]

const data = [
  ["az", 20],
  ["ad", 50]
].reduce((r, [key, value]) => {
  r[key] = (r[key] || 0) + value;
  return r;
}, {})

const expected = defaultData.map(([key, value]) => {
  return [key, key in data ? data[key] : value] 
})

console.log(expected)

answered Apr 25, 2019 at 13:48

Nenad Vracar

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Comments

Ashish Ranjan · Accepted Answer · 2019-04-25 13:56:06Z

1

Try this out, I am using map() to create a new Array and find() to find elements from the second array.

I compare the first index item of each sub array from the default array, if any of the items from second array has the same element in its first index then I return it, if none matches, nothing is returned.

If I have a matched item then I create a new array using its elements. If I don't have a matched item I create a new using the default elements of the default item.

const defaultData = [
  ["ad", 0],
  ["ae", 0],
  ["af", 0]
]

const data = [
  ["az", 20],
  ["ad", 50]
]

let newData = defaultData.map(eachDefault => {
  let found = data.find(eachData => {
    if (eachData[0] == eachDefault[0]) {
      return true
    }
  })
  if (found) {
    return [...found]
  }
  return [...eachDefault]
})

console.log(newData)

edited Apr 25, 2019 at 13:56

answered Apr 25, 2019 at 13:47

Ashish Ranjan

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1 Comment

Maheer Ali Over a year ago

Answers saying "Try this out:" are not appreciated. You should explain your code.

Fraction · Accepted Answer · 2019-04-25 14:08:02Z

1

You can use map/reduce like this:

const defaultData = [
  ["ad", 0],
  ["ae", 0],
  ["af", 0]
]

const data = [
  ["az", 20],
  ["ad", 50]
]

const result = defaultData.map(arr => data.reduce(([dKey, dVal], [key, val]) => [ dKey, dKey === key ? val : dVal ], arr));

console.log(result);

answered Apr 25, 2019 at 14:08

Fraction

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