CouchDB映射中有哪些JavaScript函数可用，并减少视图函数？ [英] What JavaScript functions are available in the CouchDB map and reduce view functions?
问题描述
在JavaScript中为CouchDB编写map和reduce视图函数时，有哪些可用的内置函数？
When writing map and reduce view functions for CouchDB in JavaScript, what are the build-in functions available?
例如，各种示例涉及以下2个函数： emit（键，值）和 sum（values）。还有其他功能，如 avg（值）可用吗？
For example, various examples refer to the following 2 functions: emit(key, value) and sum(values). Are there other functions like avg(values) available?
我在哪里可以找到所有可用功能的完整列表？
Where can I find a full list of all functions available?
推荐答案
我不知道CouchDB的内部结构，但是，通过阅读源代码，看起来地图函数是< a 已评估 https://github.com/apache/couchdb/blob/trunk/share/server/loop.js#L16\"rel =nofollow> init_sandbox（） 。因此可用的全局函数是您看到的添加到它的函数。例如：
I don't know the CouchDB internals, however, from reading the sources, it looks like the map functions are evaluated in the sandbox created by init_sandbox(). So the available "global" functions are the ones you see added to it. For example:
require()log()isArray()sum()- ...
_sum 和 _count 内置缩减功能，你只能按原样使用它们。
_sum and _count, instead, are built-in reduce functions written in Erlang, and you can only use them as-is.
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