React+es6下的webpack.config.js怎么写

参考github上面的示例：
https://github.com/newtriks/generator-react-webpack

'use strict';
let opts = require('./configopts.json');

/**
* Get a setting
* @param {String} setting
* @return {Mixed} setting or null if not found
*/
let getSetting = (setting) => {
return opts[setting] !== undefined ? opts[setting] : null;
}

/**
* Get choices for a given setting
* @param {String} setting
* @return {Mixed} Result or null if nothing was found
*/
let getChoices = function getChoices(setting) {

let config = getSetting(setting);
return config && Array.isArray(config.options) ? config.options : null;
}

/**
* Get the wanted choice by key
* @param {String} setting
* @param {String} key
* @return {Object}
*/
let getChoiceByKey = (setting, key) => {

let choices = getChoices(setting);
if(!choices) {
return null;
}

let result = null;

for(let choice of choices) {

if(choice.name === key) {
result = choice;
break;
}
}

return result;
}

/**
* Get the default choice for a config setting
* @param {String} setting
* @return {Mixed}
*/
let getDefaultChoice = (setting) => {
let config = getSetting(setting);
return config && config.default !== undefined && config.default.length > 0 ? config.default : null;
}

// getChoices
// getDefault

module.exports = {
getSetting: getSetting,
getChoices: getChoices,
getChoiceByKey: getChoiceByKey,
getDefaultChoice: getDefaultChoice
};