这个require.js 和其他的有什么区别吗

Question

下面是个require.js，我们项目（一个ionic项目）里用到的，google得到的信息也不多。
上网查了一下，得知有什么nodejs按照CommonJS实现的requirejs，还有AMD规范的requirejs，但是我们项目里用的是下面的这个require.js，用法和AMD的写法不一样，和nodejs的比较像，而且用gulp也能对这个进行打包，我想问问这到的是个什么东西，还有它说是Smoothie的一部分，不知道这个Smoothie是个什么项目。兼容性貌似也不是很好，Android5.0以下是不支持这玩意的，如果我想兼容个IE8(或者放宽到IE9也行)什么的，在浏览器的环境下有什么requireJS能够供我选择呢？

//
// This file is part of Smoothie.
//
// Copyright (C) 2013-2015 Flowy Apps GmbH <hello@flowyapps.com>
//
// Smoothie is free software: you can redistribute it and/or modify it under the
// terms of the GNU Lesser General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option) any
// later version.
//
// Smoothie is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
// details.You should have received a copy of the GNU Lesser General Public
// License along with Smoothie.  If not, see <http://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////////////

// INFO Standalone require()
//      This is a stripped down standalone version of Smoothie's require
//      function. If you also like to have a 'bootloader', which gives you some
//      nice hooks to execute code on different loading states of the document
//      and keeps your JavaScript completely separate from your HTML, we
//      recommend to load smoothie.js from the library's root directory.

// NOTE The load parameter points to the function, which prepares the
//      environment for each module and runs its code. Scroll down to the end of
//      the file to see the function definition.
(function(load) { 'use strict';

var SmoothieError = function(message, fileName, lineNumber) {
    this.name = "SmoothieError";
    this.message = message;
}
SmoothieError.prototype = Object.create(Error.prototype);

// NOTE Mozilla still sets the wrong fileName porperty for errors that occur
//      inside an eval call (even with sourceURL). However, the stack
//      contains the correct source, so it can be used to re-threw the error
//      with the correct fileName property.
// NOTE Re-threwing a new error object will mess up the stack trace and the
//      column number.
if (typeof (new Error()).fileName == "string") {
    self.addEventListener("error", function(evt) {
        if (evt.error instanceof Error) {
            if (pwd[0]) {
                evt.preventDefault();
                throw new evt.error.constructor(evt.error.message, pwd[0].uri, evt.error.lineNumber);
            }
            else {
                var m = evt.error.stack.match(/^[^\n@]*@([^\n]+):\d+:\d+/);
                if (m === null) {
                    console.warn("Smoothie: unable to read file name from stack");
                }
                else if (evt.error.fileName != m[1]) {
                    evt.preventDefault();
                    throw new evt.error.constructor(evt.error.message, m[1], evt.error.lineNumber);
                }
            }
        }
    }, false);
}

// INFO Current module descriptors
//      pwd[0] contains the descriptor of the currently loaded module,
//      pwd[1] contains the descriptor its parent module and so on.

var pwd = Array();

// INFO Path parser
// NOTE Older browsers don't support the URL interface, therefore we use an
//      anchor element as parser in that case. Thes breaks web worker support,
//      but we don't care since these browser also don't support web workers.

var parser = URL ? new URL(location.href) : document.createElement('A');

// INFO Module cache
// NOTE Contains getter functions for the exports objects of all the loaded
//      modules. The getter for the module 'mymod' is name '$name' to prevent
//      collisions with predefined object properties (see note below).
//      As long as a module has not been loaded the getter is either undefined
//      or contains the module code as a function (in case the module has been
//      pre-loaded in a bundle).
// NOTE IE8 supports defineProperty only for DOM objects, therfore we use a
//      HTMLDivElement as cache in that case. This breaks web worker support,
//      but we don't care since IE8 has no web workers at all.

try {
    var cache = new Object();
    Object.defineProperty(cache, "foo", {'value':"bar",'configurable':true});
    delete cache.foo;
}
catch (e) {
    console.warn("Falling back to DOM workaround for defineProperty: "+e);
    cache = document.createElement('DIV');
}

// INFO Send lock
// NOTE Sending the request causes the event loop to continue. Therefore
//      pending AJAX load events for the same url might be executed before
//      the synchronous onLoad is called. This should be no problem, but in
//      Chrome the responseText of the sneaked in load events will be empty.
//      Therefore we have to lock the loading while executing send().   

var lock = new Object();

// INFO Smoothie options
//      The values can be set by defining a object called Smoothie. The
//      Smoothe object has to be defined before this script here is loaded
//      and changing the values in the Smoothie object will have no effect
//      afterwards!

var requirePath = self.Smoothie&&self.Smoothie.requirePath!==undefined ? self.Smoothie.requirePath.slice(0) : ['./'];
var requireCompiler = self.Smoothie&&self.Smoothie.requireCompiler!==undefined ? self.Smoothie.requireCompiler : null;

// NOTE Parse module root paths
var base = [location.origin, location.href.substr(0, location.href.lastIndexOf("/")+1)];
for (var i=0; i<requirePath.length; i++) {
    parser.href = (requirePath[i][0]=="."?base[1]:base[0])+requirePath[i];
    requirePath[i] = parser.href;
}

// NOTE Add preloaded modules to cache
for (var id in (self.Smoothie && self.Smoothie.requirePreloaded))
    cache['$'+resolve(id).id] = self.Smoothie.requirePreloaded[id].toString();

// NOTE Add module overrides to cache
for (var id in (self.Smoothie && self.Smoothie.requireOverrides))
    cache['$'+resolve(id).id] = self.Smoothie.requireOverrides[id];

// INFO Module getter
//      Takes a module identifier, resolves it and gets the module code via an
//      AJAX request from the module URI. If this was successful the code and
//      some environment variables are passed to the load function. The return
//      value is the module's `exports` object. If the cache already
//      contains an object for the module id, this object is returned directly.
// NOTE If a callback function has been passed, the AJAX request is asynchronous
//      and the mpdule exports are passed to the callback function after the
//      module has been loaded.

function require(identifier, callback, compiler) {
    if (identifier instanceof Array) {
        var modules = new Array();
        var modcount = identifier.length;
        for (var index = 0; index < identifier.length; index++) {
            (function(id, i) {
                modules.push(require(id, callback&&function(mod) {
                    modules[i] = mod;
                    (--modcount==0) && callback(modules);
                }, compiler));
            })(identifier[index], index);
        }
        return modules;
    }

    compiler = compiler!==undefined ? compiler : requireCompiler;
    var descriptor = resolve(identifier);
    var cacheid = '$'+descriptor.id;

    if (cache[cacheid]) {
        if (typeof cache[cacheid] === 'string')
            load(descriptor, cache, pwd, cache[cacheid]);
        // NOTE The callback should always be called asynchronously to ensure
        //      that a cached call won't differ from an uncached one.
        callback && setTimeout(function(){callback(cache[cacheid])}, 0);
        return cache[cacheid];
    }

    var request = new XMLHttpRequest();

    // NOTE IE8 doesn't support the onload event, therefore we use
    //      onreadystatechange as a fallback here. However, onreadystatechange
    //      shouldn't be used for all browsers, since at least mobile Safari
    //      seems to have an issue where onreadystatechange is called twice for
    //      readyState 4.
    callback && (request[request.onload===null?'onload':'onreadystatechange'] = onLoad);
    request.open('GET', descriptor.uri, !!callback);
    lock[cacheid] = lock[cacheid]++||1;
    request.send();
    lock[cacheid]--;
    !callback && onLoad();
    return cache[cacheid];

    function onLoad() {
        if (request.readyState != 4)
            return;
        if (request.status != 200)
            throw new SmoothieError("unable to load "+descriptor.id+" ("+request.status+" "+request.statusText+")");
        if (lock[cacheid]) {
            console.warn("module locked: "+descriptor.id);
            callback && setTimeout(onLoad, 0);
            return;
        }
        if (!cache[cacheid]) {
            var source = compiler ? compiler(request.responseText) : request.responseText;
            load(descriptor, cache, pwd, 'function(){\n'+source+'\n}');
        }
        callback && callback(cache[cacheid]);
    }
}

// INFO Module resolver
//      Takes a module identifier and resolves it to a module id and URI. Both
//      values are returned as a module descriptor, which can be passed to
//      `fetch` to load a module.

function resolve(identifier) {
    // NOTE Matches [1]:[..]/[path/to/][file][.js]
    var m = identifier.match(/^(?:([^:\/]+):)?(\.\.?)?\/?((?:.*\/)?)([^\.]+)?(\..*)?$/);
    // NOTE Matches [1]:[/path/to/]file.js
    var p = (pwd[0]?pwd[0].id:"").match(/^(?:([^:\/]+):)?(.*\/|)[^\/]*$/);
    var root = m[2] ? requirePath[p[1]?parseInt(p[1]):0] : requirePath[m[1]?parseInt(m[1]):0];
    parser.href = (m[2]?root+p[2]+m[2]+'/':root)+m[3]+(m[4]?m[4]:'index');
    var uri = parser.href+(m[5]?m[5]:'.js');
    if (uri.substr(0,root.length) != root)
        throw new SmoothieError("Relative identifier outside of module root");
    var id = (m[1]?m[1]+":":"0:")+parser.href.substr(root.length);
    return {'id':id,'uri':uri};
}

// INFO Exporting require to global scope

if (self.require !== undefined)
    throw new SmoothieError('\'require\' already defined in global scope');

try {
    Object.defineProperty(self, 'require', {'value':require});
    Object.defineProperty(self.require, 'resolve', {'value':resolve});
    Object.defineProperty(self.require, 'path', {'get':function(){return requirePath.slice(0);}});
}
catch (e) {
    // NOTE IE8 can't use defineProperty on non-DOM objects, so we have to fall
    //      back to unsave property assignments in this case.
    self.require = require;
    self.require.resolve = resolve;
    self.require.path = requirePath.slice(0);
}

})(

// INFO Module loader
//      Takes the module descriptor, the global variables and the module code,
//      sets up the module envirinment, defines the module getter in the cache
//      and evaluates the module code. If module is a bundle the code of the
//      pre-loaded modules will be stored in the cache afterwards.
// NOTE This functions is defined as an anonymous function, which is passed as
//      a parameter to the closure above to provide a clean environment (only
//      global variables, module and exports) for the loaded module. This is
//      also the reason why `source`, `pwd` & `cache` are not named parameters.
// NOTE If we would strict use mode here, the evaluated code would be forced to be
//      in strict mode, too.

function /*load*/(module/*, cache, pwd, source*/) {
    var global = self;
    var exports = new Object();
    Object.defineProperty(module, 'exports', {'get':function(){return exports;},'set':function(e){exports=e;}});
    arguments[2].unshift(module);
    Object.defineProperty(arguments[1], '$'+module.id, {'get':function(){return exports;}});
    arguments[3] = '('+arguments[3]+')();\n//# sourceURL='+module.uri;
    eval(arguments[3]);
    // NOTE Store module code in the cache if the loaded file is a bundle
    if (typeof module.id !== 'string')
        for (id in module)
            arguments[1]['$'+require.resolve(id).id] = module[id].toString();
    arguments[2].shift();
}

);