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reduce: Throw TypeError if the channel contains no values and initialValue is not provided.

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David Braun 2017-10-13 21:32:27 -04:00
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@ -257,6 +257,21 @@ value has been shifted out or placed in the buffer.
reserved value used to indicate a closed channel.
#### reduce(callbackfn[, initialValue])
`callbackfn` should be a function that takes two arguments (unlike `Array`'s
version which takes four). `reduce` calls the callback, as a function, once for
each value after the first value present in the channel.
`callbackfn` is called with two arguments: the `previousValue` (value from the
previous call to `callbackfn`) and the `currentValue`. The first time that
callback is called, the `previousValue` and `currentValue` can be one of two
values. If an `initialValue` was provided in the call to `reduce`, then
`previousValue` will be equal to `initialValue` and `currentValue` will be equal
to the first value in the channel. If no `initialValue` was provided, then
`previousValue` will be equal to the first value in the channel and
`currentValue` will be equal to the second. It is a `TypeError` if the channel
contains no values and `initialValue` is not provided.
#### shift() -> async
Returns a promise that resolves when an value is received from the channel.