Run a node shell script in --harmony mode

Question

How can I run a globally-installed node module that exposes a shell script in --harmony mode?

Answer 1

TL;DR: Just use Node 5+, most ES6 features will be availble right away.

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2016 answer

This is more like an amendment to the 2015 answer.
The reason is because Node.js and io.js have converged, and the project is now a lot stronger, having lots of updates while keeping Long-Term Support (LTS) and supporting lots of ES6 features, in addition to those that io.js did support as well.

Notable features available in Node.js 5.0.0+:

• new.target
• Spread operator
• Arrow functions
• Object.assign

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2015 answer

We now have io.js available. It's reliable, fast, and up-to-date with the stable ES6 specs.

Depending on what ES6 features you want, you can use it with no flag at all. From their website:

• Block scoping
  • let
  • const
  • function-in-blocks

    As of v8 3.31.74.1, block-scoped declarations are intentionally implemented with a non-compliant limitation to strict mode code. Developers should be aware that this will change as v8 continues towards ES6 specification compliance.

• Collections
  • Map
  • WeakMap
  • Set
  • WeakSet
  • Generators
• Binary and Octal literals
• Promises
• New String methods
• Symbols
• Template strings

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2014 answer

What about spawning a second Node process with your stuff?

#!/usr/bin/env node

var spawn = require("child_process").spawn;
var child = spawn(process.execPath, [ "--harmony", "yourscript.js" ], {
  cwd: __dirname
});

child.stdout.on("data", function( data ) {
  console.log(data);
});

child.stderr.on("data", function( data ) {
  console.error(data);
});

EDIT: I believe process.execPath returns the node path, not the global script path in this case.
However, you can always change it to node directly, but that could break installations without node in the PATH.