问题
First the question:
Where can I find the external-helpers.js script, or how can I build the external-helpers for Babel 6?
In Babel 5.x, I was able to use the externalHelpers option, which required including external-helpers.js, which used to be in the babel-core package. Moving on to Babel 6, I see that external-helpers is now external-helpers-2 plugin. This does the job of including the relevant babelHelper calls in my transpiled code, but that is it; I need the actual helper definitions!
In the issue add missing build script for external-helpers.js, it is suggested to " build it yourself with the CLI". I don't see any CLI options that seem to deal with building external helpers.
回答1:
I managed to build the external-helpers.js with the babel-core package and the Node REPL:
var helperBuilder = require('./lib/tools/build-external-helpers');
fs.writeFileSync('external-helpers.js', helperBuilder());
I imagine that, depending on your situation, you could also build the external helpers file by build script (Grunt, Gulp, etc.)
回答2:
The CLI command referred to in the issue you mention is babel-external-helpers, which is part of the babel-cli npm package. With the babel-cli package installed, running babel-external-helpers --help gives the following self-explanatory output:
Usage: babel-external-helpers [options]
Options:
-h, --help output usage information
-l, --whitelist [whitelist] Whitelist of helpers to ONLY include
-t, --output-type [type] Type of output (global|umd|var)
It simply outputs the file to stdout, so to print the code to a file, you do babel-external-helpers [options] > babel-helpers.js.
来源：https://stackoverflow.com/questions/33703919/how-to-use-babel-6-external-helpers-in-the-browser