Simplify implementation of extractUniqueTagsObject()

[stuarteberg]

Here's my suggested implementation, inspired in part from the discussion in the code review meeting.

• Guard clause to avoid deep indentation
• Perform deduplication using Set instead of explicit includes check.
• I assume validTagKeys.includes(key) is preferable to validTagKeys.some(...), but maybe I'm missing something.
• I removed the global tagKeyNames, since I think it's clearer to the reader to see its definition inline.
• Use the "make this an array if it isn't already" trick within the loop, too. Reduces the number of if/else blocks.
  • As discussed in the meeting, whether to use a new variable name or reuse the old one is a stylistic choice. Your call, of course.

I tested this implementation in my browser's dev console:

test setup

function extractUniqueTagsObject(contentCollection) {
    const uniqueTags = {};
    const validTagKeys = Object.keys(validTagsList);

  // For each key, determine the union of all unique values associated with it
  // (across all content items), excluding keys which aren't in validTagsList.
  contentCollection = Array.isArray(contentCollection) ? contentCollection : [contentCollection];
  contentCollection.forEach((contentItem) => {
    Object.entries(contentItem.data).forEach(([key, tagValues]) => {
      if (!validTagKeys.includes(key) || !tagValues || !tagValues.length) {
        return;
      }
      uniqueTags[key] ??= new Set();
      tagValues = Array.isArray(tagValues) ? tagValues : [tagValues];
      tagValues.forEach((tv) => {
        uniqueTags[key].add(tv);
      });
    });
  });

  // Convert from Sets to sorted Arrays
  Object.keys(uniqueTags).forEach((key) => {
    uniqueTags[key] = Array.from(uniqueTags[key]).sort();
  });
  return uniqueTags;
}

validTagsList = {
  pet: 'foo',
  robot: 'bar'
}
contentCollection = [
  {
    data: {
      invalid: 'invalid',
      pet: ['dog', 'cat'],
      robot: 'vacuum'
    }
  },
  {
    data: {
      pet: 'cat',
      robot: ['vacuum', 'flyflipper']
    }
  }
];
​
result = extractUniqueTagsObject(contentCollection);
console.log(JSON.stringify(result, null, 2));

It produces the following output:

{
  "pet": [
    "cat",
    "dog"
  ],
  "robot": [
    "flyflipper",
    "vacuum"
  ]
}

[github-actions]

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[allison-truhlar]

Thanks for working on this, Stuart. The extractUniqueTagsObject function is much more readable now!