The letters, (+), (+) before the endings are typical letters of the. However, there are verbs that form the without these letters, as you will see below. In the the verbs are in principle stressed on the third-to-last syllable...

Para ello, vamos a basarnos en un código JavaScript de Stack Overflow, que según he entendido y probado funciona en la mayoría de navegadores y sin necesidad de JQuery.