refresh_coursera_token_postman_pre_request_script.js

/*
  Install this script as a pre-request Script on your Postman collection.
  Define Auth_Url, and Basic_Auth as local variables on the collection.
  Define OAuth_Token, OAuth_Timestamp, ExpiresInTime, OAUTH_USERNAME, OAUTH_PASSWORD and OAUTH_REFRESH_TOKEN 
  in the associated Postman environment.
*/
var tokenDate = new Date(2010, 1, 1);
var tokenTimestamp = pm.environment.get("OAuth_Timestamp");
if (tokenTimestamp) {
  tokenDate = Date.parse(tokenTimestamp);
}
var expiresInTime = pm.environment.get("ExpiresInTime");
if (!expiresInTime) {
  expiresInTime = 1800; 
}
if ((new Date() - tokenDate) >= expiresInTime) {
  pm.sendRequest({
    url: pm.variables.get("Auth_Url"),
    method: 'POST',
    header: {
      'Accept': 'application/json',
      'Content-Type': 'application/x-www-form-urlencoded',
      'Authorization': pm.variables.get("Basic_Auth")
    },
    body: {
      mode: 'urlencoded',
      urlencoded: [
        { key: "grant_type", value: "refresh_token", disabled: false },
        { key: "client_id", value: pm.environment.get("OAUTH_USERNAME"), disabled: false },
        { key: "client_secret", value: pm.environment.get("OAUTH_PASSWORD"), disabled: false },
        { key: "refresh_token", value: pm.environment.get("OAUTH_REFRESH_TOKEN"), disabled: false }
      ]
    }
  }, function (err, res) {
    pm.environment.set("OAuth_Token", res.json().access_token);
    pm.environment.set("OAuth_Timestamp", new Date());

    if (res.json().expires_in) {
      expiresInTime = res.json().expires_in * 1000;
    }
    pm.environment.set("ExpiresInTime", expiresInTime);
  });
}