check if some source code uses syntax supported by an ES version

You can use this before eg. running Babel with a million transforms on a file. Note that this attempts to parse the file using acorn, so it is pretty slow; recommended to memoize the result!

npm install is-es-version

var isEsVersion = require('is-es-version')

isEsVersion('const a = 10', 5) // false
isEsVersion('var a = 10', 5) // true

Check if src is a source code string that is supported by the EcmaScript version version. The default version is 5. Returns true if the syntax is supported by the given version; false if not.

Set opts.parser to use a custom parser module, such as acorn-node.

isEsVersion('#!/usr/bin/env node\nrequire("./lib/cli")', 5, { parser: require('acorn-node') })

Apache-2.0