As the title suggests, I am trying to create a single array of strings:

['string1', 'string2', 'string3']

Out of an array of objects with arrays of strings within those objects:

[
  {
    array_of_strings: ['string1', 'string2', 'string3']
  },
  {
    array_of_strings: ['string1', 'string4', 'string5']
  },
  {
    array_of_strings: ['string6', 'string3', 'string2']
  }
]

As you can see there is a possibility that the nested arrays may contain the same strings as each other, and I am trying to de-duplicate at the same time. I got very lost in map, filter and reduce. But nothing really outputs the data as needed.

Any guidance would be appreciated.

CodePudding user response：

You can use a javascript Set for this, check the docs

const array = [
  {
    array_of_strings: ["string1", "string2", "string3"],
  },
  {
    array_of_strings: ["string1", "string4", "string5"],
  },
  {
    array_of_strings: ["string6", "string3", "string2"],
  },
];

const result = array.reduce((acc, { array_of_strings }) => {
  return acc.concat(array_of_strings);
}, []);

const unique = new Set(result);

const uniqueArray = Array.from(unique);

console.log(uniqueArray);

CodePudding user response：

First you want to "regroup" all of thoses strings together in the same array :

const fullDatas = [
  {
    array_of_strings: ["string1", "string2", "string3"],
  },
  {
    array_of_strings: ["string1", "string4", "string5"],
  },
  {
    array_of_strings: ["string6", "string3", "string2"],
  },
];

const allStrings = fullDatas.reduce((acc, currentValue)) => {
  return acc.concat(currentValue.array_of_strings);
}, []);

then you can have a look at this thread

and use it :

const uniq = [...new Set(allStrings)];

CodePudding user response：

You need none of map/filter/reduce :-) Use flatMap, then deduplicate:

const data = [
  {
    array_of_strings: ['string1', 'string2', 'string3']
  },
  {
    array_of_strings: ['string1', 'string4', 'string5']
  },
  {
    array_of_strings: ['string6', 'string3', 'string2']
  }
];

const result = Array.from(new Set(data.flatMap(o => o.array_of_strings)));
console.log(result);

CodePudding user response：

If I understand your question correctly(to get all the elements appear more than once),we can use Array.filter() ,Array.reduce(), Array.map() to do it

let data = [
  {
    array_of_strings: ['string1', 'string2', 'string3']
  },
  {
    array_of_strings: ['string1', 'string4', 'string5']
  },
  {
    array_of_strings: ['string6', 'string3', 'string2']
  }
]

data = data.map(d => d.array_of_strings).flat().reduce((a,v) =>{
  a[v] = a[v]??0
  a[v]  = 1
  return a
},{})

let result = Object.entries(data).filter(i => i[1] > 1).map(i => i[0])
console.log(result)