Question 53562 in Javascript Question posted in
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Iterate over set and remove element if it is in another set and return array – Javascript

I am not sure what I am missing from my function here to remove elements in a a set. It seems the loop is not working as expected. If you have a more optimal solution O(1), please share. Thanks!

const dupArr = ["a", "b", "c", "d", "d",'dog']

function transformSearchFields(fields) {
  let noDupes = new Set(fields)
  const searchData = new Set(['dog', 'a'])

  // iterate over noDupes set and check if element is in the searchData set. If it is, remove the element from the noDupes set
  noDupes.forEach(element => {
    if (element in searchData) {
        noDupes.delete(element)
    }
  })

  return [...noDupes]
  }
// desired output: ["b", "c", "d"]

I expected the loop to remove values that were in the searchData set

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4

Answers


  1. 0

    Here is example how you can filter an array with unique values in response:

    const inputArray = ['a', 'b', 'c', 'd', 'd', 'dog'];
const dataToReject = ['dog', 'a'];

const filteredUniqueArray = [...new Set(
  inputArray.filter(inputArrayElement =>
    !dataToReject.some(dataToRejectElement => 
      inputArrayElement == dataToRejectElement
    )
  )
)];

console.log(filteredUniqueArray); // ['b', 'c', 'd']
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  2. 0

    To check if a value is "in" a Set, use .has()

    .has

    The has() method returns a boolean indicating whether an element with the specified value exists in a Set object or not.

    In your case this would be:

    if (searchData.has(element)) {

    Updated snippet

    const dupArr = ["a", "b", "c", "d", "d", 'dog']

function transformSearchFields(fields) {
  let noDupes = new Set(fields)
  const searchData = new Set(['dog', 'a'])

  // iterate over noDupes set and check if element is in the searchData set. If it is, remove the element from the noDupes set
  noDupes.forEach(element => {
    //console.log(element, element in searchData, searchData.has(element))
    if (searchData.has(element)) {
      noDupes.delete(element)
    }
  })

  return [...noDupes]
}
console.log(transformSearchFields(dupArr));

    There are other methods filter data (as provided in other answer, so not repeated here).

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  3. 0

    You could take the Set directly and omit items of this the for filtering.

    function transformSearchFields(fields) {
    return fields.filter(
        (s => v => !s.has(v) && s.add(v))
        (new Set(['dog', 'a']))
    );
}

console.log(transformSearchFields(["a", "b", "c", "d", "d", 'dog'])); // b c d
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  4. 0

    You can convert your dupArr Set to array again with spread operator and use filter with the has method for your searchData Set

    const transform = (fields, searchData) => [...new Set(fields)].filter(el => !searchData.has(el));


const searchData = new Set(['dog', 'a']);
const dupArr = ["a", "b", "c", "d", "d",'dog']

console.log(transform(dupArr,searchData));
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