Call NodeJS from Julia.
Author sunoru
19 Stars
Updated Last
11 Months Ago
Started In
June 2021


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Call NodeJS from Julia.

Currently supports NodeJS v18 (Latest LTS) on 64-bit Linux and macOS platforms.


This package depends on libnode_jll.jl and libjlnode_jll.jl.

You need to have Julia v1.7+ installed to use this package.


] add NodeCall

It's recommended to test the package before using it:

] test NodeCall


With NodeCall.initialize(), a NodeJS instance will start in the current process. A new V8 Virtual Machine context (vm in the standard library of NodeJS) is automatically created.

And JavaScript code can be run with node_eval or @node_str (they are equivalent except the latter supports interpolation):

julia> using NodeCall

# This is not required if you are using NodeCall from REPL.
julia> NodeCall.initialize();

julia> node_eval("console.log('Hello, world!')")
Hello, world!

julia> x = 5;
julia> node"2 * $x"

You can directly use require to use Node APIs.

julia> os = require("os");

julia> os.type()

To install a package from NPM, use something like this:

julia> NPM.install("boxen");

added 19 packages, and audited 20 packages in 683ms

11 packages are looking for funding
  run `npm fund` for details

found 0 vulnerabilities

Note that it is equivalent to running npm install in the current working directory, but with the specific version of NodeJS provided by NodeCall.jl.

And then you can use the installed package as if you are writing JavaScript. In this example, node_import or @node_import should be used since boxen is an ES Module.

# `node_import` is like the function-like dynamic import in JS, so it is asynchronous and should be awaited.
julia> boxen = (@await node_import("boxen")).default;

# or you can use module style import declaration with `@node_import` macro.
julia> @node_import boxen from "boxen";

julia> boxen("Generated in JS") |> println
│Generated in JS│

# To pass an option object, the easiest way is to use a `NamedTuple` in Julia:
julia> boxen("Passing options", (padding=1, borderStyle="double")) |> println
║                     ║
║   Passing options   ║
║                     ║

# Alternatively, you can just use a node string:
julia> boxen("Passing a JS Object", node"{padding: 1}") |> println
│                         │
│   Passing a JS Object   │
│                         │

See examples/ or test/runtests.jl for more examples.

Known Issues

One important problem of NodeCall.jl is that it cannot work with Julia's multi-thread/process functions, as well as the asynchronous methods involving Tasks. However, asynchronous features in NodeJS (Promises) works fine by awaiting them explicitly.

You can now use @threadsafe f(args...) to make/call a function in a threadsafe manner.

You have to use @await instead of wait or fetch to wait for a Task to finish if the Task accesses the NodeJS environment, since it calls run_node_uvloop automatically.

Another way to asynchronously access the NodeJS environment is to use @node_async. @node_async works like @async in Julia, but instead of scheduling a Task in Julia, it creates a JsPromise to wait on. Thus, the tasks are managed by the NodeJS side.

jl_yield() is automatically called in NodeJS' event loop, so it won't block other Tasks in Julia.

Bug Reports & Contributing

Please feel free to file issues and pull requests. Any feedback or help would be greatly appriciated.

To contribute, you can firstly have a look at the TODO list.

It may also be helpful to edit the C++ code in jlnode to define some utility functions. It is mainly because in pure Julia it is difficult to handle pointers, especially those of functions.


MIT License

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