Betty White has been a TV star as long as there’s been TV.

Hired by a pioneering L.A. broadcaster, she made her tube debut in February 1939. Standing under hot lights in a primitive sixth-floor studio, the teen performed a number from “The Merry Widow.” The show was brief and local.

Really local.

“The picture went all the way down to the lobby,” White said.

But the experimental transmission beat NBC’s first broadcast from the New York World’s Fair by two months. And it marked the official beginning of a career that would carry the perky performer through several hit TV series and eight Emmys.

So far.

As Ray Richmond’s “Betty White: 100 Remarkable Moments in an Extraordinary Life” suggests, the 99-year-old isn’t done yet.

White grew up in California, an only child in a quirky family. Her father, an electrical engineer, had a side business selling radios. Except few people had extra cash during the Great Depression, so he accepted dogs as payment.

“The dogs ate and the radios didn’t,” White recalled. “It wasn’t the best business decision he ever made.”

It made their daughter a life-long animal lover. That ease around beasts came in handy in 1949. That’s when the young radio actress branched out, making her onscreen debut in “The Daring Miss Jones.” Her co-stars? A couple of rambunctious bear cubs.

It didn’t lead to a film career, but TV — in its infancy — offered more extensive opportunities. Later that year, White landed a job co-hosting a local program called “Hollywood on Television,” a mix of interviews, comedy sketches, and music.

Immediately popular, the show was soon running Monday through Saturday, from 12:30 to 6 p.m., for 33 hours of live TV a week. And White was on for every minute of it.

“It was like going to television college,” she said. “We could do anything we wanted. Whatever happened, happened on camera. Like playing an improv game every day — except it was going out live.”

White won an Emmy for the show and early praise for her comedic skills. Soon, a recurring sketch on the show was spun-off as a separate sitcom, 1953′s “Life With Elizabeth.” White starred and produced and hired another woman, Betty Turbiville, to direct.

“I never found it a handicap to be a female back then,” she said of those pioneering days. “Maybe I just didn’t know any better.”

But one job was never enough for White. While the sitcom was shooting, she started a daytime talk program, “The Betty White Show.”

Controversy soon loomed, however. One of the regulars was a young Black tap dancer, Arthur Duncan. Objecting to the on-air integration, Southern stations demanded Duncan be cut from the show.

White’s response? She used him more often.

“Fortunately, NBC backed up the show’s stance,” Richmond writes. “Though the network perhaps didn’t convey Betty’s exact sentiments, which were of the ‘shove it’ variety.”

White’s busy career continued smoothly, though her personal life was rockier. By 1961, the 39-year-old was divorced twice and described herself as “militantly single.”

Then she was a guest contestant on a new daytime game show, “Password.” The host, Allen Ludden, was recently widowed with three children. White felt a connection but fought it — at first.

Ludden sensed an undeniable spark, too. When he was cast in a summer-stock production of “Critic’s Choice,” he asked the producers to sign White as his co-star. He then began courting her in earnest and even enlisted his kids to try to persuade her to marry him.

Finally, in 1963, White said yes. They were happily married for 18 years. After Ludden died from cancer, White returned to being “militantly single” — and remained so.

“He was the love of my life,” she explained. “If you’ve had the best, who needs the rest?”

As the 1960s went on, though, White’s career slowed a little. She was a frequent and favorite talk-show guest and game-show contestant, but people seemed to forget how talented an actress she was.

“Once you get into the talk routine, producers don’t want to trust you as an actress,” she noted. “They forget you started out as an actress.”

However, casting director Renee Valente remembered. When she saw a script for “The Mary Tyler Moore Show” described a character as an “icky sweet Betty White type, but also as vicious as a barracuda,” Valente suggested they hire the real woman — White.

Sue Ann Nivens was created. What was supposed to be a one-off guest appearance for White turned into a regular gig.

“She was so great, so inventive, that we couldn’t wait to have her back on,” Moore explained. “She became everyone’s delicious pixie. She represented all the evil places and dark corners we have inside us, and we cheered her on.”

After “The Mary Tyler Moore Show” ended, White moved on to her own sitcom, “The Betty White Show.” Oddly, though, instead of having her repeat her beloved character — as MTM stars Valerie Harper, Ed Asner and Cloris Leachman all had — she was to play someone new, a struggling TV actress.

The show was canceled after 14 episodes.

“I nearly derailed her career with my stupidity,” co-creator Ed. Weinberger acknowledges.

“To this day I have no idea why I did that or what I was thinking,” he says about not simply reusing the Sue Ann Nivens character. “If there is a television hell, I will be going there.”

But White, as always, kept going. She did “Love Boat” episodes. She guest-starred on “Mama’s Family.” Finally, in 1985, she signed on for a new ensemble comedy, “The Golden Girls.” She would play Blanche, the aging sexpot. Rue McClanahan was up for Rose, the naïve farmgirl.

Then the producing team had a last-minute brainstorm: Have the stars switch roles.

“How can you do this to me?” moaned White, who already had prepared for the other part. But the change-up was genius. And in White’s hands, Rose became the sweet, daffy heart of the show, which ran until 1992. It even spawned a brief spin-off, “The Golden Palace.”

When that went off the air, too, White was 70. But why slow down now?

She joined another sitcom, “Maybe This Time.” When that went belly-up, she did a campy giant crocodile movie, “Lake Placid,” and signed on for a stint on “Boston Legal.” She briefly joined a soap, “The Bold and the Beautiful,” then returned for another hit sitcom, “Hot in Cleveland.”

White isn’t merely busy — she’s in the Guinness Book of World Records, having “appeared as a regular or recurring player on more shows than any actress in prime-time history,” Richmond writes.

It’s a medium she continues to enliven with commercial gigs, talk-show appearances, and even, by popular demand — remember that Facebook campaign — hosting “Saturday Night Live.” And why not? She’s having almost as good of a time acting as audiences experience watching her.

“I can claim one thing I don’t know anyone else can claim, and I do it wholeheartedly,” she said in 1995, as she was inducted into the Television Academy Hall of Fame. “Nobody — nobody — has had more fun in this world doing what they do for a living than I have.”

Jacqueline Cutler writes for the New York Daily News.