Van Alexander, the 1940s bandleader who co-wrote “A-Tisket, A-Tasket” with Ella Fitzgerald and went on to score dozens of films and TV shows in the 1950s and ’60s, died of heart failure Sunday afternoon at Cedars-Sinai Medical Center in Los Angeles. He was 100.

A three-time Emmy nominee for composition and music direction in the early 1970s, Alexander was head arranger for the entire run of NBC”s “Dean Martin Show” (1965-74) and wrote scores for many 1960s sitcoms including “Hazel,” “The Donna Reed Show,” “Dennis the Menace,” “The Farmer’s Daughter,” “Bewitched” and “I Dream of Jeannie.”

He was also the composer of more than a dozen 1950s and ’60s film scores including “The Atomic Kid,” “Baby Face Nelson,” “Andy Hardy Comes Home,” “Girls Town” and a trio of William Castle films that have become cult favorites: “13 Frightened Girls,” “Strait-Jacket” and “I Saw What You Did.”

Alexander was the author of “First Arrangement,” a landmark 1946 how-to book for musicians learning how to arrange for orchestra. He later penned an autobiography, “From Harlem to Hollywood: A Life in Music.”

He was born in New York, May 2, 1915, and began piano lessons at the age of 6. He became friendly with bandleader Chick Webb at Harlem’s Savoy Ballroom and sold his first arrangement at the age of 19.

Webb’s featured singer Fitzgerald suggested the idea of making the nursery rhyme “A-Tisket, A-Tasket” into a jazz number, and they recorded it on Alexander’s 23rd birthday in 1938. It became her first big hit and his biggest hit as a songwriter. He went on to write band arrangements for Benny Goodman and Bob Crosby.

Alexander led his own band from 1939 to 1944, moving to L.A. in 1945 and starting to compose for films in the 1950s. His work on “The Atomic Kid” and TV’s “The Mickey Rooney Show,” both in 1954, led to a series of scores for Rooney films into the 1960s.

Over the years, Alexander worked with singers including Gordon MacRae, Peggy Lee, Dinah Shore, Doris Day, Mitzi Gaynor, Lena Horne, Bob Hope, Tony Bennett and others.

In television, Alexander worked as music director on numerous 1960s and ’70s variety specials including ones headlined by Gene Kelly, Dom DeLuise and Jonathan Winters. His Emmy noms were for Winters and Kelly shows and Martin’s summer-replacement series “The Golddiggers.”

Alexander was a past president of the American Society of Music Arrangers and Composers, and served on its board of directors for many years. He received lifetime-achievement awards from the Los Angeles Jazz Society in 1997, Pacific Pioneer Broadcasters in 1997 and the ASCAP Foundation in 2002.

Alexander celebrated his 100th birthday at an all-star bash in May at Catalina Bar & Grill, attended by more than 200 members of the jazz, film and TV music community.

His wife Beth, to whom he was married for 72 years, died in 2010. He is survived by two daughters, Joyce Harris and Lynn Tobias of Los Angeles, four grandchildren, and 14 great-grandchildren.

Services will be at 12 noon Wednesday at Hillside Memorial Park Cemetery.