What's the deal with China's $1 trillion foreign exchange reserve

I heard China has a dollar reserve of over $1 trillion, which is larger than Japan's. It seems the Chinese government spends a lot of taxpayers' money on foreign stocks and bonds to keep the yuan cheap. The other week, it was reported that the Chinese also bought a large stake in BlackRock, and that the yuan had fallen to a 15-year low with a bearish outlook. I can't help but think that China is acting in bad faith and draining the value of its currency to artificially inflate its GDP.