调试器中未定义ES6模块导入 [英] ES6 module import is not defined during debugger

问题描述

在与Babel和Webpack玩耍的同时，我今天偶然发现了一些非常奇怪的行为。

While playing around with Babel and Webpack I stumbled into some really weird behavior today.

我在我的 main.js 中投掷了一个调试器，以查看我是否正确导入，但Chrome的控制台不停地叫喊我正在尝试导入的模块未定义。我尝试控制台记录相同的模块，我看到它打印到我的控制台。

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.

什么给了？我已经粘贴了相关的代码片段：

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' }
        ]
    }
};

推荐答案

tl; dr： Babel不一定保存变量名称。

tl;dr: Babel does not necessarily preserve variables names.

如果我们看代码生成从

import Thing from './Thing.js';

debugger;

console.log(new Thing());

即：

'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']());

我们看到事物没有确定。所以Chrome是正确的。

We see that Things is not defined indeed. So Chrome is correct.

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