He practiced in Shanghai from the mid-1930s onward, starting at the Universal Building & Engineering Co, and then branching out on his own.
His office was always located in the Associate Mission Building, at 169 Yuen Ming Yuen Road.
Hajek taught western architectural history at St. John's University in the 1940s and 1950s.
He was still lingering in Shanghai as late as 1957...
But honestly – which of his buildings do you wish to have been realised?
Proposed Pere Robert Apartments, 1934:
Proposed office building for Whangpoo Road, 1934:
Plan for the "Central Building" on Nanking Road, 1935:
Proposed design of the Racecourse Apartments, end of 1935:
These proposals were also published in 1935:
(note the different Chinese spelling of his name, 海其渴)
He got a commission to design a cluster of villas on Columbia Road, west of the French Concession, at the end of 1935:
This villa on Hongqiao Road is also his creation of 1935:
Here is a letter sent to Sweden in 1957, from "海傑克 Professor Architect Dipl. Eng. Hans J. Hajek, B.A., M.B., C.E., M.A.A.S., 169 Yuen Ming Yuen Road, Shanghai, China":