javascript.....判斷 global

/** Detect free variable `global` from Node.js. */
  var freeGlobal = typeof global == 'object' && global && global.Object === Object && global;

  /** Detect free variable `self`. */
  var freeSelf = typeof self == 'object' && self && self.Object === Object && self;

  /** Used as a reference to the global object. */
  var root = freeGlobal || freeSelf || Function('return this')();
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 // node.js

if (typeof exports != 'undefined' && !exports.nodeType) {
        if (typeof module != 'undefined' && !module.nodeType && module.exports) {
            exports = module.exports = _;
        }
        exports._ = _;
    } else {
        root._ = _;
    }






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// node.js

  /** Detect free variable `exports`. */
  var freeExports = typeof exports == 'object' && exports && !exports.nodeType && exports;

  /** Detect free variable `module`. */
  var freeModule = freeExports && typeof module == 'object' && module && !module.nodeType && module;

  /** Detect the popular CommonJS extension `module.exports`. */
  var moduleExports = freeModule && freeModule.exports === freeExports;

  /** Detect free variable `process` from Node.js. */
  var freeProcess = moduleExports && freeGlobal.process;

  /** Used to access faster Node.js helpers. */
  var nodeUtil = (function() {
    try {
      // Use `util.types` for Node.js 10+.
      var types = freeModule && freeModule.require && freeModule.require('util').types;

      if (types) {
        return types;
      }

      // Legacy `process.binding('util')` for Node.js < 10.
      return freeProcess && freeProcess.binding && freeProcess.binding('util');
    } catch (e) {}
  }());
---------------------------------------------------

var root = this
// AMD / RequireJS
if (typeof define !== 'undefined' && define.amd) {
    define([], function () {
        return async;
    });
}
// Node.js
else if (typeof module !== 'undefined' && module.exports) {
    module.exports = async;
}
// included directly via <script> tag
else {
    root.async = async;
}