Javier began his musical career in the late 1960s. He was already dabbling in performing solo and with other groups when he enrolled at the
Ateneo de Manila University for college. He became part of a singing group named Danny, Mandy, and Alice, with Mandy Marquez and Alice Zerrudo. In 1970, Javier met
Jim Paredes,
Boboy Garrovillo,
Ric Segreto, and 9 other original members of the Apolinario Mabini Hiking Society or known today as
Apo Hiking Society. Although he was a latecomer to the group, remember the members had been together since high school and in some cases, even grade school, Danny instantly became the lead vocalist. The group was formed and had its fledgling beginnings in 1969 at the
Ateneo de Manila High School. After graduation, the majority of its members left to pursue individual careers, with only three members remaining, made up of Javier, Paredes, and Garrovillo. In the span of their professional career, Apo Hiking Society emerged as a principal adherent of the musical movement termed
Original Pilipino Music (
OPM), a term coined by Javier, a milieu in which their original musical contributions and cultural influence became essential. He became involved in record production, talent management and organizing artists under the Organisasyon ng Pilipinong Mang-aawit (O.P.M., acronym translation: "
Organization of Philippine Singers/musicians"). The group expanded its activities into establishing and furthering the careers of new OPM artists in the Philippines. As a television actor, Javier was part of different shows and movies such as
Kung Mangarap Ka't Magising (1977),
Kakabakaba Ka Ba? (1980), Blue Jeans (1981), and
I Do Bidoo Bidoo: Heto nAPO Sila! (2012). Javier, with Paredes and Garrovillo, managed to host their own shows such as
Sa Linggo nAPO Sila (
They Are Now On Sunday), a Philippine musical-variety show that aired on ABS-CBN from December 3, 1989, to January 29, 1995, replaced by the first Talent Singing competition show
Tawag ng Tanghalan from 1987–1989, and
'Sang Linggo nAPO Sila (
They Are Now On All Week), a Philippine daily noon-time variety show of
ABS-CBN that aired from January 28, 1995, to November 28, 1998, replacement of
Eat Bulaga! and followed by Magandang Tanghali Bayan or MTB. To date, the Apo Hiking Society has released 27 albums and hundreds of songs over a career spanning four decades. Two hugely successful tribute albums were produced in 2006 and 2007 by its management group, featuring numerous young bands reinterpreting APO's expansive repertoire, included many hit songs such as "
When I Met You", "
Panalangin", "
Batang-Bata Ka Pa", "
Yakap Sa Dilim", "
Pumapatak Ang Ulan", "
Ewan", "
Handong Ng Pilipino Sa Mundo", "
Awit Ng Barkada", "
Mahirap Magmahal Ng Syota Ng Iba", "
Paano", "
Pag-ibig", "
Nakapagtataka", "
Di Na Natuto", "
Show Me A Smile", "
Blue Jeans", "''Tuyo Na'ng Damdamin
", "Kumot At Unan
", "Kaibigan
", "Sa'n Na Nga Ba'ng Barkada Ngayon
", "Bawat Bata"
, "Princesa
", "American Junk
", "Lumang Tugtugin
", "Salawikain
", "Doo Bidoo''", and many among others. In 2010, the Apo Hiking Society, composed of Javier, Paredes, and Garrovillo decided to retire as a group after 41 years of activity. They performed a series of farewell concerts that started on February 14, 2010, and ended in May, just in time for the elections. In 2018, He retired from both singing and acting. ==Personal life and death==