You can find the text of Japji Sahib in Punjabi at SikhiWiki.org The site contains the text of the prayer in Gurumukhi script, as well as an English translation version.
The word "Jap" means "to recite," "to repeat," "to chant" and "to understand." The Japji Sahib is a Sikh prayer composed by Guru Nanak Dev, the first Guru of the Sikhs and the founder of Sikhism. It appears at the beginning of Guru Granth Sahib, the sacred scripture of Sikhism. The Japji Sahib provides a discourse on the true nature of worship, and it states that God is indescribable and the only true form of worship is the acceptance of God; to seek to be one with him. Traditionally, the prayer is used at the Sikh initiation ceremony as well as the cremation ritual.