Perform a union on two sets - test not passing but seems to work?

JavaScript
1

I think I have completed this correctly - but I cannot pass the tests. I’m obviously missing something but I have no idea any more what. My console.logs appear to give me the result I am seeking - that is to say I create a set containing {'a', 'b', 'c'} and then call the union method with ['c', 'd'] as the argument. The new set created returns - correctly I think - { dictionary: { a: 'a', b: 'b', c: 'c', d: 'd' }, length: 4 }.

Any ideas?

class Set {
  constructor() {
    // This will hold the set
    this.dictionary = {};
    this.length = 0;
  }
  // This method will check for the presence of an element and return true or false
  has(element) {
    return this.dictionary[element] !== undefined;
  }
  // This method will return all the values in the set
  values() {
    return Object.values(this.dictionary);
  }
  // This method will add an element to the set
  add(element) {
    if (!this.has(element)) {
      this.dictionary[element] = element;
      this.length++;
      return true;
    }

    return false;
  }
  // This method will remove an element from a set
  remove(element) {
    if (this.has(element)) {
      delete this.dictionary[element];
      this.length--;
      return true;
    }

    return false;
  }
  // This method will return the size of the set
  size() {
    return this.length;
  }
  // Only change code below this line
  union(setB) {
    console.log(setB)
    const newSet = new Set();
    console.log(newSet)
    this.values().forEach(value => newSet.add(value))
    console.log(newSet)
    if (setB.length) setB.forEach(value => newSet.add(value))
    console.log(newSet)
    return newSet
  }
  // Only change code above this line
}

And the way I have been calling it to test it works:

const obj = new Set()
obj.add('a')
obj.add('b')
obj.add('c')
obj.union(['c','d'])

Challenge: Perform a Union on Two Sets

Link to the challenge:

2

The forEach part of these two lines should be identical except for the set over which they are iterating.

3

Thanks Jeremy. I forgot to say I had already tried that. The if was just to check that there wasn’t a test condition being passed with null length.

Removing the if statement like so still doesn’t pass the test.

union(setB) {
    console.log(setB)
    const newSet = new Set();
    this.values().forEach(value => newSet.add(value))
    setB.forEach(value => newSet.add(value))
    return newSet
  }
4

Not the if. The first one is this.values().forEach(...) and the second is setB.forEach(...). The second one is missing something.

5

Thanks again Jeremy. I see what you mean, but this.values() and setB are both arrays.

To prove it, I have changed to the following:

union(setB) {
    console.log('setA', Object.values(this.dictionary))
    console.log('setB', Object.values(setB))
    const newSet = new Set();
    console.log('newSet', newSet)
    Object.values(this.dictionary).forEach(value => newSet.add(value))
    console.log(newSet)
    Object.values(setB).forEach(value => newSet.add(value))
    console.log(newSet)
    return newSet
  }

const obj = new Set()
obj.add('a')
obj.add('b')
obj.add('c')
obj.union(['c','d'])

returns

setA [ 'a', 'b', 'c' ]
setB [ 'c', 'd' ]
newSet { dictionary: {}, length: 0 }
{ dictionary: { a: 'a', b: 'b', c: 'c' }, length: 3 }
{ dictionary: { a: 'a', b: 'b', c: 'c', d: 'd' }, length: 4 }

This still does not pass, but I have no idea what is wrong.

6

No, it is not an array, it’s a Set(). Your original code produces the following messages when the tests run:

{ dictionary: { c: 'c', d: 'd' }, length: 2 }
{ dictionary: {}, length: 0 }
{ dictionary: { a: 'a', b: 'b', c: 'c' }, length: 3 }
{ dictionary: { a: 'a', b: 'b', c: 'c', d: 'd' }, length: 4 }

The first line the output of console.log(setB). That’s not an array, that’s a Set() object and calling its values() method will give you the array of values, as your new code shows.

You can even try an example

let setC = new Set();
setC.add(1);
setC.add(2);
setC.add(3);
setC.forEach((item) => console.log(item));

outputs TypeError: setC.forEach is not a function while setC.values().forEach((item) => console.log(item)); outputs

1
2
3

So, this line of your original code

is still not correct. Further, if you try/catch that line of code like

    try {
      if (setB.length) setB.forEach(value => newSet.add(value))
    } catch (error) {
      console.log(error);
    }

the error thrown is TypeError: setB.forEach is not a function, just like my example. So, that is the problem.

Plus, I fixed this very line the other day and that was the only change needed to pass…

7

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