index.js

const core = require('@actions/core');
const github = require('@actions/github');

async function run() {
    try {
        const token = core.getInput('token', { required: true });
        const reviewers = core.getInput('reviewers');
        const user_reviewers = reviewers.split(',');
        const team_reviewers = core.getInput('team_reviewers');
        const slug_reviewers = team_reviewers.split(',');
        const octokit = github.getOctokit(token);
        const context = github.context;

        if (context.payload.pull_request == null) {
            core.setFailed("No pull request found.");
            return;
        }

        const owner = context.repo.owner;
        const repo = context.repo.repo;
        const pr_number = context.payload.pull_request.number;

        if (reviewers) {
            const params = {
                owner: owner,
                repo: repo,
                pull_number: pr_number,
                reviewers: user_reviewers,
            }
            await octokit.rest.pulls.requestReviewers(params);
        }
        
        else if (team_reviewers) {
            const params = {
                owner: owner,
                repo: repo,
                pull_number: pr_number,
                team_reviewers: slug_reviewers,
            }
            await octokit.rest.pulls.requestReviewers(params);
        }

        else if (reviewers && team_reviewers) {
            const params = {
                owner: owner,
                repo: repo,
                pull_number: pr_number,
                reviewers: user_reviewers,
                team_reviewers: slug_reviewers,
            };
            await octokit.rest.pulls.requestReviewers(params);
        }

        else {
            console.log("No reviewers or team reviewers specified");
        }
    } catch (error) {
        core.setFailed(error.message);
    }
}

run();