Incorrect documentation for fixing memory leaks

The "isMounted is an Antipattern" documentation article suggest avoiding memory leaks with makeCancelable, but this doesn't actually solve the issue since the callback is still referenced. The garbage collector does not understand that setting hasCanceled_ means that resolve will never be called, so it cannot release resolve or the references contained within. Even if it could, reject might also reference this, so memory leaks could still exist. Instead, makeCancelable should store the resolve and reject callbacks itself, and it should null them out on cancelation.

Another user pointed this issue out in https://github.com/facebook/react/issues/5465#issuecomment-287113777

受影响的材料是 issue 中链接的“isMounted is an Antipattern”文章；首先查看其中的 makeCancelable 示例以及所引用的讨论。更新文档，使其关于内存泄漏的指导在技术上正确，然后确认该文章不再推荐存在争议的实现。