How can I retrieve the reputation I (or another user, fwiw) earned for a given tag from questions and answers?

Question

(I've included the api-v2.3 because https://api.stackexchange.com/docs starts with Stack Exchange API v2.3.)

From this answer I see there's no way to get all questions with a specific tag.

However, what about all questions/answers asked/answered by a user with a specific tag?

To avoid this question to be an example of the XY problem, I want to clarify that my final target is to be able to show on a personal site the reputation I earned on this or that tag.

I see the API provides

• a /users/{ids}/questions method to query for all questions from given user identities;
• a /users/{ids}/answers method to query for all answers from given user identities;
• a /questions/{ids} method to query for a question given its id.

On the one hand, questions come with a tags field, whereas answers do not. On the other hand, answers come with a question_id.

Therefore, I think I could do the following:

1. For questions

   1.1. make the /users/{ids}/questions request;

   1.2 filter the obtained questions based on a specific tag;

   1.3. extract the score field from each question;

   1.4. sum up all entries.

2. For answers

   2.1 make the /users/{ids}/answers request;

   2.2 for each of them, get the question_id;

   2.3 for each question_id, make a new request using the /questions/{ids} method;

   2.4 on the array of questions, apply steps from 1.2 to 1.4 above.

Then the two amounts would be added up and multiplied by 10.

---

However, before venturing, I'd like some feedback on whether I'm taking the correct route or not.

Answer 1

As a more involved alternative, there is a dedicated endpoint for retrieving reputation changes - /reputation. It returns a list of Reputation objects, each having a post_id and reputation_change field. This is the only accurate metric for counting reputation changes - score field does not represent this information accurately for various reasons (including retroactive changes to vote weight by SE - yes, it happened before).

After retrieving the list of reputation changes, you need to extract the post ids, uniquify them (to avoid extra API calls as the query is heavy as is), fetch the /questions batch endpoint to get the list of questions, filter by tag, and map the result to a list of ids.

Then the only thing you need to do is to filter the reputation changes depending on whether the post_id is present in the abovementioned list or not. This will yield you reputation changes for bounties, suggested edits, and questions. The only thing left is getting changes for answers, but I leave that as an exercise for the reader.

The following snippet demonstrates how one could convert this idea into working code:

Important note: depending on your activity levels, the number of API calls might be a little heavy, please account for that if you are an avid userscript user and thus have to be weary about the daily quota usage

const API_VER = 2.3;
const API_BASE = "https://api.stackexchange.com";

const sleep = (sec = 1) => new Promise((r) => setTimeout(r, sec * 1e3));
const uniquify = (arr) => [...new Set(arr)];

const getQuestions = async(postIds, {
  site = "stackoverflow",
  page = 1,
  ...rest
}) => {
  const url = new URL(`${API_BASE}/${API_VER}/questions/${postIds.join(";")}`);
  const params = new URLSearchParams({
    site,
    page: page.toFixed(0),
    ...rest,
  });
  url.search = params.toString();
  const res = await fetch(url.toString());
  if (!res.ok)
    return [];
  const {
    items = [], has_more = false, backoff,
  } = (await res.json());
  if (backoff) {
    await sleep(backoff);
    return getQuestions(postIds, {
      site,
      page,
      ...rest
    });
  }
  if (!has_more)
    return items;
  const more = await getQuestions(postIds, {
    page: page + 1,
    site,
    ...rest,
  });
  return [...items, ...more];
};

const getReputation = async(userIds, {
  page = 1,
  site = "stackoverflow",
  ...rest
}) => {
  const url = new URL(`${API_BASE}/${API_VER}/users/${userIds.join(";")}/reputation`);
  const params = new URLSearchParams({
    site,
    page: page.toFixed(0),
    ...rest,
  });
  url.search = params.toString();
  const res = await fetch(url.toString());
  if (!res.ok)
    return [];
  const {
    items = [], has_more = false, backoff,
  } = (await res.json());
  if (backoff) {
    await sleep(backoff);
    return getReputation(userIds, {
      site,
      page,
      ...rest
    });
  }
  if (!has_more)
    return items;
  const more = await getReputation(userIds, {
    page: page + 1,
    site,
    ...rest,
  });
  return [...items, ...more];
};

const partition = (arr, perPart = 1) => {
  const parts = Math.ceil(arr.length / perPart);
  const partitions = [];
  for (let i = 0; i < parts; i++) {
    const start = i * perPart;
    partitions.push(arr.slice(start, start + perPart));
  }
  return partitions;
};

(async() => {
  const useridInput = document.getElementById("user_id");
  const siteInput = document.getElementById("site");
  const tagInput = document.getElementById("tag");
  const progress = document.getElementById("load");

  const submit = document.getElementById("search");
  submit.addEventListener("click", async() => {
    progress.value = 0;

    const tag = tagInput.value;
    const uids = [+useridInput.value];
    const site = siteInput.value;
    const key = "zhhhBNmsqZLZ967tc2dn8w((";
    
    const common = { key, site, pagesize: 100 };

    const changes = await getReputation(uids, common);
    
    progress.value = 35;

    const postIds = uniquify(changes.map(({
      post_id
    }) => post_id));

    const partitionedIds = partition(postIds, 100);
    const results = await Promise.all(partitionedIds.map((i) => getQuestions(i, common)));
    const questions = results.flat();
    
    progress.value = 70;
    
    const tagged = questions.filter(({
      tags = []
    }) => tags.includes(tag));
    const taggedIds = tagged.map(({
      question_id
    }) => question_id);
    const relevantChanges = changes.filter(({
      post_id
    }) => taggedIds.includes(post_id));
    const totals = {
      up: 0,
      down: 0,
      tag
    };
    relevantChanges.forEach(({
      reputation_change
    }) => {
      totals[reputation_change > 0 ? "up" : "down"] += Math.abs(reputation_change);
    });
    
    progress.value = 100;
    
    const up = document.getElementById("up");
    const down = document.getElementById("down");
    
    up.textContent = totals.up;
    down.textContent = totals.down;
  });
})();

label {
  display: block;
  font-weight: 600;
}

caption,
label {
  font-weight: 600;
  margin: 1vh 0;
}

input {
  display: block;
}

button, progress {
  margin-top: 2vh;
  margin-bottom: 2vh;
}

<form>
  <label for="site">Site API slug</label>
  <input id="site" type="text" title="API slug" placeholder="stackoverflow" value="stackoverflow" />

  <label for="user_id">User Id</label>
  <input id="user_id" type="text" title="User Id" placeholder="12345" value="" />

  <label for="tag">Tag Name</label>
  <input id="tag" type="text" title="Tag Name" placeholder="typescript" value="" />

  <button id="search" type="button">Get Changes</button>
</form>

<progress id="load" max="100" value="0"></progress>

<p>Up: <span id="up"></span></p>
<p>Down: <span id="down"></span></p>

Answer 2

It is easier to use the /users/{id}/top-tags (JSON) endpoint for a single user.

That will give you for a given user all their tags with score and count for question and answers. Don't let the "top" misguide you. The user I used as an example has 440 tags in the API result and that is roughly 50 tags off compared to their site profile (and SEDE). Close enough I would say.

{
  "items": [
    {
      "user_id": 811,
      "answer_count": 176,
      "answer_score": 10331,
      "question_count": 0,
      "question_score": 0,
      "tag_name": "javascript"
    },
    {
      "user_id": 811,
      "answer_count": 37,
      "answer_score": 4211,
      "question_count": 0,
      "question_score": 0,
      "tag_name": "html"
    },
    {
      "user_id": 811,
      "answer_count": 95,
      "answer_score": 4031,
      "question_count": 0,
      "question_score": 0,
      "tag_name": "jquery"
    },

Do notice the default filter doesn't include Total in the wrapper, so you have to add that field if you want to know upfront how many pages you have to fetch.