New York (CNN Business) Signs that the world economy is starting to weaken have alarmed investors. Some global companies have warned of a slowdown in China. But things are looking good for Nike.

Nike's sales surged 10% in the three months that ended November 30 from the same quarter a year ago, the company said Thursday. That included a 26% increase in China, thanks to sales from the country's Black Friday-like Singles Day and demand for sneakers like Air Jordan.

Nike ( NKE ) is considered a bellwether of the broader economy. Its stock has fallen 18% over the last three months during the wider market slide . Shares rallied 7% after hours.

Investors are worried about the possibility of Chinese tariffs on clothing and sneakers, which would strike at Nike, the world's largest sportswear company.

The Chinese economy has weakened lately, in part from the trade war between Beijing and Washington. The dollar has strengthened against the yuan, which makes US products more expensive for Chinese consumers. Last month, Tiffany said Chinese tourists were spending less on jewelery.

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