node-version-cli

Conditionally pass arguments on the command line depending on the current version of node.

Install

$ npm install --global node-version-cli

Usage

Example: only use the babel compiler if running node <4.0.0

$ mocha $(node-version --lt-4.0.0 --compilers js:babel/register)

Version Conditions

• --gte-0.2.0: greater than or equal to 0.2.0
• --lte-3.0.0: less than or equal to 3.0.0
• --gt-0.5.0: greater than 0.5.0
• --lt-0.6.0: less than 0.6.0
• --eq-1.0.0: exactly equal too 1.0.0

Output

Any argument not matching the Version Condition pattern described above is considered to be an output argument.

In general the pattern is:

node-version condition1 condition2 outputA outputB condition3 outputC

The program outputs the following:

• If only conditions 1 and 2 are satisfied: outputA outputB
• If only condition 3 is satisfied: outputC
• If all conditions are satisfied: outputA outputB outputC
• If only 1 or 2 or none are satisfied: <empty output>

Failure Conditions and Exit Codes

If the final arguments are Version Conditions (i.e. conditions not followed byOutput), failure to satisfy the conditions will cause a VersionConditionError to be thrown and the process to exit with a non-zero error code.

You can use this with the bash || operator to skip commands for some versions.

node-version --lt-3.0.0 || node-version --gte-4.0.0 || npm run node-3-only-tests

Note that using || means the following command runs only when the conditions fail. Running only when the conditions pass is doable, but a bit more convoluted. It is often easier to just invert your condition and stick to using ||.

Command Substitution

When combined with Command Substitution this becomes a powerful construct for controlling how bash scripts behave.

The original intended use was disabling the babel compiler for mocha tests running in newer versions of node (which already support some ES6 features).

$ mocha $(node-version --lt-4.0.0 --compilers js:babel/register)

The stack trace is often obfuscated when using the babel compiler (the line numbers won't match up).

Getting rid of babel improves performance, and gives nice stack traces on Node 4+. This scripts allows you to continue running your CI tests against old versions of Node.

License

MIT © James Talmage