pre-request

postman-pre-request.js

const echoPostRequest = {
  url: pm.environment.get('baseUrl') + '/login',
  method: 'POST',
  header: 'Content-Type:application/json',
  body: {
    mode: 'application/json',
    raw: JSON.stringify(
      {
        "mail": "asd@amazon.com",
        "password": "HXtaSUzh"
      })
  }
};
pm.sendRequest(echoPostRequest, function (err, res) {
  var responseJson = res.json();
  pm.environment.set('token', responseJson.token)
});

// to update variables, use tests
var data = pm.response.headers.get("x-access-token");
pm.environment.set('token', data);