Clear Arrays by pushing an empty array

[onyx-blackbird]

Let's start with this simple DataLayer object:

{
  page: {
    campaigns: ['campaign1', 'campaign2']
  }
}

Then I push this:

adobeDataLayer.push({
  page: {
    campaigns: []
  }
});

Expected Behaviour

adobeDataLayer.getState() returning this:

{
  page: {
    campaigns: []
  }
}

Actual Behaviour

adobeDataLayer.getState() returning this:

{
  page: {
    campaigns: ['campaign1', 'campaign2']
  }
}

Workaround

You need to push null to delete it before setting it to an empty array as described above.

adobeDataLayer.push({
  page: {
    campaigns: null
  }
});

The other way would be to first find out how many items there are in the array already and do a push like this:

adobeDataLayer.push({
  page: {
    campaigns: [null, null]
  }
});

[L-Triple-O]

I'm also seeing this issue and with updating arrays in general. Attempting to update an existing array of:
campaigns: ['camp-one', 'camp-two']
with an update of:
campaigns: ['camp-one']
will still result in a datalayer with:
campaigns: ['camp-one', 'camp-two']
when calling adobeDataLayer.getState()

Is this by design or a bug? I was expecting any update in general to be valid.

[jm-adobe]

Just curious about this issue, but would you mind describing the need to clear these arrays?

[L-Triple-O]

@jm-adobe in a case of wanting clear an array or pass new information on an event to the dataLayer. This also seems to be a possibility described in the documentation yet overwrite may not work as expected? .. One important detail to clarify is what happens when pushing data to an already existing array: it will overwrite the data of the inner array.