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The replique module provides a server which can evaluate separate chunks of code in a persistent environment.

It can also perform REPL-like completion.

Multiple contexts are supported, allowing the use of multiple REPLs on the same server instance without namespace conflicts.

replique was developed for use with the vim addon noderepl, but functions as a general server, responding to JSON-formatted requests. For information on how to make requests, see the Protocol section.

It can also be used in combination with the Python poste_replique module. poste_replique provides a CLI and Python API for interaction with replique.

Note that there is not yet a client written for node.


To start a replique server, run

$ node src/node-replique.js

The server will open port 4994.

It is not currently possible to set the port with a command-line parameter. It is possible to use a different port by calling the API.

For example, to run a server on port 1337:

$ node
> new (require('replique').Server)().listen(1337);

Subsequently, console output (including, for now, debug logging messages) will be printed.


The replique protocol consists of requests and responses made in JSON format.

A typical exchange looks like this:


{ command: 'evaluate',
  code: '["hello", "world"].join(" ")'


{ command: 'evaluate',
  result: 'success',
  value: '"hello world"'

A context attribute can also be supplied. If present, its value should be a string containing the name of the evaluation context to be used. If it is not given, the default context ("default") will be used.

The commands complete and uniqueContext are also available.

complete performs completion as done by node's built-in repl. The attributes in the JSON request should be the same ones, with context being optional.

uniqueContext can be used to generate a new, uniquely-named context. Unique context names are formed by incrementing a numeric suffix and appending it to an optional prefix. This is useful to avoid name clashes with existing contexts. A uniqueContext request can, in addition to the command attribute, include the context attribute. In this case its value will be used as the prefix. Otherwise, the context name will just be a number.

The server will respond as soon as it receives a chunk of data which concludes a string of properly-formed JSON data.

The properties of the responses vary by command and result. See the test suite for a thorough set of examples.


Parsing of the requests is implemented by attempting to decode repeatedly concatenated chunks of data, which is not particularly efficent if there are multiple chunks for a single command.

Additionally, parsing displays the same somewhat wonky behaviour as node's built-in REPL. See node issue #807 for details.