URI.js fragment overloading for seamless `!/some/path` and `?some=data` handling

URI.fragment.js

/*
 * Extending URI.js for fragment abuse
 */

// --------------------------------------------------------------------------------
// EXAMPLE: storing a relative URL in the fragment ("FragmentURI")
// possibly helpful when working with backbone.js or sammy.js
// inspired by https://github.com/medialize/URI.js/pull/2
// --------------------------------------------------------------------------------

// Note: make sure this is the last file loaded!

// USAGE:
// var uri = URI("http://example.org/#!/foo/bar/baz.html");
// var furi = uri.fragment(true);
// furi.pathname() === '/foo/bar/baz.html';
// furi.pathname('/hello.html');
// uri.toString() === "http://example.org/#!/hello.html"

(function (root, factory) {
    // https://github.com/umdjs/umd/blob/master/returnExports.js
    if (typeof exports === 'object') {
        // Node
        module.exports = factory(require('./URI'));
    } else if (typeof define === 'function' && define.amd) {
        // AMD. Register as an anonymous module.
        define(['./URI'], factory);
    } else {
        // Browser globals (root is window)
        factory(root.URI);
    }
}(this, function (URI) {
"use strict";

var p = URI.prototype;
// old handlers we need to wrap
var f = p.fragment;
var b = p.build;

// add fragment(true) and fragment(URI) signatures    
p.fragment = function(v, build) {
    var fragment = this._parts.fragment || "";
    var prefix = fragment.slice(0, 1);
    var furi;

    if (v === true) {
        if (prefix === '!') {
            // remove prefix for regular URIs
            furi = new URI(fragment.slice(1) || "");
        } else {
            // keep the prefix as it's just a query string
            furi = new URI(fragment);
        }
        
        this._fragmentURI = furi;
        furi._parentURI = this;
        return furi;
    } else if (v instanceof URI) {
        this._fragmentURI = v;
        v._parentURI = this;
        var s = v.build(false)._string;
        if (s.slice(0, 1) === '?') {
            // the prefix ? is already given by v.toString()
            prefix = '';
        } else {
            // FIXME: ! is always added, this may be a problem
            prefix = '!';
        }
        this._parts.fragment = prefix + s;
        this.build(!build);
        return this;
    } else if (typeof v === "string") {
        this._fragmentURI = undefined;
    }

    return f.call(this, v, build);
};

// make .build() of the actual URI aware of the FragmentURI
p.build = function(deferBuild) {
    var t = b.call(this, deferBuild);
    
    if (deferBuild !== false && this._parentURI) {
        // update the parent
        this._parentURI.fragment(this);
    }

    return t;
};

// extending existing object rather than defining something new
return {};
}));