Apple (Nasdaq: AAPL) shares are on watch following positive commentary in the WSJ.

The Journal noted how Apple's success in China is due, in part, to the company's iPhone trade-in program. The program helps to narrow the price premium for an iPhone in China and has helped Apple to boost its market share in the country.

Those purchasing an iPhone in China tend to want to keep the device looking newer, longer. One example is that most try to utilize the "Assistive Touch" feature on the device, which is intended for those with disabilities that make it difficult to press the Home button on the iPhone. Usage of the feature helps keep the Home button looking new over the life of the device.

Consumers also utilize screen covers for the iPhone, which has become so commonplace that vendors set up shops outside of Apple stores.

The article doesn't make clear Apple's current share in China, but highlights how demand in the country is still strong even for older devices. That strength could also turn into a vulnerability as China's economy continues to taper-off from red hot growth seen over the last 20 years.

Shares of Apple are indicated for a higher open Tuesday. The company will post Q1 results after markets close today.