But a spokesman for the Foreign Ministry, Lu Kang, offered a cautious rebuttal of Mr. Trump’s views on trade between China and the United States, arguing that trade had “benefited the people on both sides, including the American people, and has increased employment, rather than the opposite.”
Some economic advisers to the Chinese government were skeptical that Mr. Trump would follow through with drastic action that could prompt a trade war. After all, they said, American presidential candidates have been promising to get tough on Chinese trade policies for more than two decades and have invariably backed off after taking office.
“Nobody takes the electioneering that seriously,” said Andrew Sheng, a former chairman of the Hong Kong Securities and Futures Commission who advises the Chinese government on financial policy. “People accept that the American consumers benefit so much from trade that it won’t change that much.”
Yu Yongding, a prominent economist at the Chinese Academy of Social Sciences in Beijing, also had doubts. “All the things he said during the election were the talk of an amateur — I don’t think he was in earnest,” he said. “After he becomes president, there’ll be advisers at his side to explain to him what the exchange rate is, what capital flows are, what macroeconomic policy is.”
But if there was disbelief that Mr. Trump would follow through on his trade threats, there was also unease that his election could portend a retreat by the United States from the region that could embolden China, force Japan and South Korea to consider alternatives to the American nuclear umbrella and unleash long-suppressed tensions.
“Maybe he will decrease the commitment to Pacific security issues,” said Shin Kawashima, a professor of international relations at the University of Tokyo. “But if he carries out such a policy, China will be much more authoritative and aggressive in the Pacific. And then most of the alliance countries and security experts in Washington will be against Trump’s policies. It is a little difficult for Trump to just change all the old policies.”
In Tokyo, Prime Minister Shinzo Abe congratulated Mr. Trump and sought to remind him of Washington’s special relationship with his nation. “Japan and the United States are unwavering allies tied firmly with the bond of universal values such as freedom, democracy, basic human rights, and the rule of law,” he said.
And some in Japan expressed hope that Mr. Trump might prove milder in office than he was on the campaign trail.
“Once he becomes the president, he will change, I think,” said Katsuhito Momii, 73, chairman of NHK, the public broadcasting service. “Reagan became a great president, so no matter what he said before the election, I think he will change.”
Some analysts said they feared that Mr. Trump’s America First vision would embolden Japan’s own right-wing nationalists, who push a revisionist history that denies the Japanese military committed atrocities during World War II. Jiro Yamaguchi, a professor of political science at Hosei University in Tokyo, said that China and South Korea, victims of Japan’s wartime aggression, would object to any resurgence of Japan’s right wing and that this would increase tensions in East Asia.
In South Korea, where President Park Geun-hye has been battling a corruption scandal, there appeared to be concern that Mr. Trump’s election might be misinterpreted by the North, which has been racing to develop nuclear weapons and had welcomed Mr. Trump’s threat to withdraw American troops from the South unless it paid more for their presence.
“North Korea should not misjudge the solidity of our alliance with the United States and our joint ability to respond” to its provocations, a government spokesman, Jeong Joon-hee, warned, adding that the South remained unshakable in its belief that it should maintain a strong military alliance with the United States.
Moon Jae-in, an opposition leader and leading contender for the presidency in the election next year, also reaffirmed his commitment to the alliance “no matter who becomes president there.”
Cheong Seong-chang, a senior analyst at the Sejong Institute in Seongnam, said Mr. Trump’s victory could “open the way for South Korea to go nuclear” with Washington’s consent to protect itself from the North.
The prospect of a nuclear arms race in Asia would certainly unsettle China. But analysts said that was one of many troubling issues that the Communist government could be forced to confront under a Trump presidency.
Shi Yinhong, a professor of international relations at Renmin University in Beijing, said that many in the foreign policy establishment had been wary of Hillary Clinton and believed Mr. Trump would be less likely to oppose President Xi’s increasingly assertive territorial claims in the South China Sea and elsewhere.
“A weakened and disorganized West like this will surely bring many more additional strategic opportunities for China, which would be even less prudent in its foreign policy, as it has been since 2013,” Mr. Shi said.
But he added that Mr. Trump’s approach to trade could cause problems for Mr. Xi when he is already struggling with an economic slowdown.
“These changes will make it more difficult for China’s economy,” he said, “in a time when it is already facing difficulties at home.”