node-compat-require

> Easily allow your Node program to run in a target node version range to maximize compatibility.

  

- If unsupported node version, installs the right version with npx and continues.
- Targeted at CLIs that want to maximize compatibility without sacrificing JS features.
- Use async / await in older versions of node.
- Optionally pin your node program to a specific version of node for extreme reproducibility.

Why

A lot of Node.js CLI programs need to support older versions of Node, and in order to do so, they either:

- Resort to using deprecated ES5 syntax and carefully make sure all dependencies follow suit.
- Require the CLI to be run via Docker which is clumsy to execute (eg. no npm install -g).
- Rely on a complicated transpilation step in order to achieve backwards compatibility.

While transpilation is great for larger projects, it's a bit of a headache, when all you really want to do is ensure your program works for end users.

> node-compat-require is the simplest way of ensuring a compatible node version without sacrificing the latest & greatest node features.

Install

This module requires node >= 4.

``bash
npm install --save node-compat-require
`

Usage

`js
const compatRequire = require('node-compat-require')

compatRequire('.', { node: '>= 8' })
`

In this example, './index.js' would be required only once the Node process is >= 8.

See the example folder for a complete example of a node program which can be run with node >= 4 but will enforce node >= 8 at runtime in order to support newer JS features like async / await and object destructuring.

API

$3

If the current node process satisfies the given requirements, returns require(path).

If the current node process does not satisfy the requirements, installs the correct version of node, re-invokes the current node program as a subprocess, and exits once the child process exits.

#### path

Type: String
Required

Path of file to require if node process satisfies constraints. This may be a relative file just like a normal node require statement.

#### opts

Type: Object
Required

##### opts.node

Type: String
Required

Required semver range for the node process.version.

Examples:

`js
compat('.', { node: '>= 8' })
compat('./bin', { node: '^6' })
compat('./lib/cmd', { node: '9' })
compat('./example/cli', { node: '7.10.0' })
compat('.', { node: '4 || >=9 || 6.0.0 - 7.0.0' })
`

##### opts.quiet

Type: Boolean
Default: false

Use this to optionally silence the npx output.

How it works

You require node-compat-require and pass a desired node semver range (like '>= 8' or '^6.0.0').

If the current process's node version satisfies that range, then node-compat-require requires the target module and returns.

If the current process does not satisfy that range, then npx is used to temporarily install the appropriate matching version of node from npm and re-run the current process as a subprocess using the temporary node executable. In this case, all commandline flags, environment variables, and stdio will be inherited from the current process. The child process will again run into node-compat-require, only this time it will require your target module normally because the version check is satisfied. Once the child process terminates, either due to successful completion or an error, node-compat-require will exit the parent process with the same exit code.

Note: it is recommended but not required for you to invoke node-compat-require at the very beginning of your program.
Note: node-compat-require needs an active internet connection for npx` to install the correct version of node.

Related

- npx - Used under the hood to execute specific versions of node from npm.
- node - NPM package bundling different versions of node for different platforms.
- node language features - Breakdown of supported features across different versions of node.

License

MIT © Travis Fischer