Pre-request Script in Postman help me get and refresh the access_token.

postman_pre_request.js

// https://learning.postman.com/docs/writing-scripts/script-references/postman-sandbox-api-reference/#sending-requests-from-scripts
const url = pm.environment.replaceIn("{{base_url}}/some/api")
const req = {
  url: url,
  method: 'POST',
  header: {
    'Content-Type': 'application/json',
    'X-Foo': 'bar'
  },
  body: {
    mode: 'raw',
    raw: JSON.stringify({
        key: 'this is json'
    })
  }
};

pm.sendRequest(req, function (err, response) {
  if (response.code === 200) {
    const data = response.json()
    pm.environment.set('access_token', data.access_token)
    return
  }
  console.log(`Error: ${response}`)
});