响应式编程是一种异步的、声名式的、面向数据流的编程范式。
异步：moand、observeable、handle；
声名式：用逻辑表述的形式组织代码；使用函数式编程范式。
数据流：将数据视作数据流的形式，并用pipeline的形式做处理。
rx是对响应式编程操作的标准化。
Each language-specific implementation of ReactiveX implements a set of operators. Although there is much overlap between implementations, there are also some operators that are only implemented in certain implementations. Also, each implementation tends to name its operators to resemble those of similar methods that are already familiar from other contexts in that language.
http://reactivex.io/documentation/operators.html#categorized