example.js

// You can keep it inside of the test but it's preferable to store such commands in cypress/support/commands.js 
// or create a separate file for related commands e.g. cypress/support/buttons.js 
// but don't forget to import it in cypress/support/index.js
Cypress.Commands.add('getLoginButton', (label) => {
  switch(label) {
    case 'login':
       return cy.get(loginBtnSelector);
    case 'register':
      return cy.get(registerBtnSelector);
  }
});

//Use it in test

it('should click on login button', () => {
  cy.getLoginButton('login').click();
});