支持的变量包括整型、浮点型的数字、字符串、数组和对象。
Supported variables include integers, floating point Numbers, strings, arrays, and objects.
map型：map是一个从一组键值对象到一组值对象的关联数组。
Map: a map is an associative array from a set of object keys to a collection of object values.
一个可观察对象是一个事件流，我们可以用数组型操作符来处理它。
An observable is a stream of events that we can process with array-like operators.
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