While playing around with Babel and Webpack I stumbled into some really weird behavior today.
I threw a debugger in my main.js
to see if I was importing correctly, but Chrome's console kept yelling that the module I was trying to import was not defined. I try console logging the same module instead, and I see it printed to my console.
What gives? I've pasted the relevant code snippets below:
main.js
import Thing from './Thing.js';
debugger // if you type Thing into the console, it is not defined
console.log(new Thing()); // if you let the script finish running, this works
thing.js
class Thing {
}
export default Thing;
webpack.config.js
var path = require('path');
module.exports = {
entry: './js/main.js',
output: {
path: __dirname,
filename: 'bundle.js'
},
module: {
loaders: [
{ test: path.join(__dirname, 'js'), loader: 'babel-loader' }
]
}
};
tl;dr: Babel does not necessarily preserve variables names.
If we look at the code generated from
import Thing from './Thing.js';
debugger;
console.log(new Thing());
namely:
'use strict';
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { 'default': obj }; }
var _ThingJs = require('./Thing.js');
var _ThingJs2 = _interopRequireDefault(_ThingJs);
debugger;
console.log(new _ThingJs2['default']());
We see that Things
is not defined indeed. So Chrome is correct.