node的require
这里是谈js的require
require('xxx')
一开始是没有缓存的，第一次require('xxx')会将函数执行然后将模块（路径）缓存。
如果xxx中有 未声明的变量直接赋值 这相当于在浏览器中这么做。
结果是 该未声明的变量成为了顶级对象的属性(global对象，在浏览器中则是window对象)
如果用到了严格模式"use strict"(严格模式需要在函数内最开头声明，也就是文件xxx的最顶端)
可以用Function("r", "regeneratorRuntime = r")(runtime);来规避
如 npm的regenerator-runtime
"use strict"
/**
* Copyright (c) 2014-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
var runtime = (function (exports) {
/* ... */
}(
// If this script is executing as a CommonJS module, use module.exports
// as the regeneratorRuntime namespace. Otherwise create a new empty
// object. Either way, the resulting object will be used to initialize
// the regeneratorRuntime variable at the top of this file.
typeof module === "object" ? module.exports : {}
));
try {
regeneratorRuntime = runtime;
} catch (accidentalStrictMode) {
console.log(accidentalStrictMode)
// This module should not be running in strict mode, so the above
// assignment should always work unless something is misconfigured. Just
// in case runtime.js accidentally runs in strict mode, we can escape
// strict mode using a global Function call. This could conceivably fail
// if a Content Security Policy forbids using Function, but in that case
// the proper solution is to fix the accidental strict mode problem. If
// you've misconfigured your bundler to force strict mode and applied a
// CSP to forbid Function, and you're not willing to fix either of those
// problems, please detail your unique predicament in a GitHub issue.
Function("r", "regeneratorRuntime = r")(runtime);
}