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Added Global prototype

This will clean up the code for providing global check and alternatives.
protolib
Mike Gerwitz 2014-06-07 21:42:22 -04:00
parent 9a22648fd9
commit 1bba35418a
4 changed files with 307 additions and 0 deletions

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@ -52,6 +52,9 @@ var can_define_prop = ( function()
} )(); } )();
exports.Global = require( './util/Global' );
/** /**
* Freezes an object if freezing is supported * Freezes an object if freezing is supported
* *

120
lib/util/Global.js 100644
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@ -0,0 +1,120 @@
/**
* Global scope handling
*
* Copyright (C) 2014 Free Software Foundation, Inc.
*
* This file is part of GNU ease.js.
*
* ease.js is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// retrieve global scope; works with ES5 strict mode
(0,eval)( 'var _the_global=this' );
// prototype to allow us to augment the global scope for our own purposes
// without polluting the global scope
function _G() {}
_G.prototype = _the_global;
/**
* Provides access to and augmentation of global variables
*
* This provides a static method to consistently provide access to the
* object representing the global scope, regardless of environment. Through
* instantiation, its API permits augmenting a local object whose prototype
* is the global scope, providing alternatives to variables that do not
* exist.
*/
function Global()
{
// allows omitting `new` keyword, consistent with ease.js style
if ( !( this instanceof Global ) )
{
return new Global();
}
// allows us to extend the global object without actually polluting the
// global scope
this._global = new _G();
}
/**
* Provides consistent access to the global scope through all ECMAScript
* versions, for any root variable name, and works with ES5 strict mode.
*
* As an example, Node.js exposes the variable `root` to represent global
* scope, but browsers expose `window`. Further, ES5 strict mode will provde
* an error when checking whether `typeof SomeGlobalVar === 'undefined'`.
*
* @return {Object} global object
*/
Global.expose = function()
{
return _the_global;
};
Global.prototype = {
/**
* Provide a value for the provided global variable name if it is not
* defined
*
* A function returning the value to assign to NAME should be provided,
* ensuring that the alternative is never even evaluated unless it is
* needed.
*
* The global scope will not be polluted with this alternative;
* consequently, you must access the value using the `get` method.
*
* @param {string} name global variable name
* @param {function()} f function returning value to assign
*
* @return {Global} self
*/
provideAlt: function( name, f )
{
if ( typeof this._global[ name ] !== 'undefined' )
{
return;
}
this._global[ name ] = f();
return this;
},
/**
* Retrieve global value or provided alternative
*
* This will take into account values provided via `provideAlt`; if no
* alternative was provided, the request will be deleagated to the
* global variable NAME, which may or may not be undefined.
*
* No error will be thrown if NAME is not globally defined.
*
* @param {string} name global variable name
*
* @return {*} value associated with global variable NAME or
* its provided alternative
*/
get: function( name )
{
return this._global[ name ];
},
};
module.exports = Global;

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@ -0,0 +1,143 @@
/**
* Tests global scope handling
*
* Copyright (C) 2014 Free Software Foundation, Inc.
*
* This file is part of GNU ease.js.
*
* ease.js is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
var _global = this;
require( 'common' ).testCase(
{
caseSetUp: function()
{
this.Sut = this.require( 'util/Global' );
this.gobj = this.Sut.expose();
this.uniq = '___$$easejs$globaltest$$';
},
/**
* Check common environments and ensure that the returned object is
* strictly equal to the global object for that environment. For
* environments that we do *not* know about, just check for a common
* object that must exist in ES3 and above.
*/
'Global object represents environment global object': function()
{
switch ( true )
{
// browser
case _global.window:
this.assertStrictEqual( this.gobj, _global.window );
break;
// Node.js
case _global.root:
this.assertStrictEqual( this.gobj, _global.root );
break;
// something else; we'll just check for something that should
// exist in >=ES3
default:
this.assertStrictEqual( this.gobj.Array, Array );
}
},
/**
* Since ease.js makes use of ECMAScript features when they are
* available, it must also find a way to gracefully degrade to support
* less fortunate environments; the ability to define alternative
* definitions is key to that.
*/
'Providing alternative will set value if name does not exist':
function()
{
var sut = this.Sut();
var field = this.uniq,
value = { _: 'easejsOK' };
sut.provideAlt( field, function() { return value; } );
this.assertStrictEqual( sut.get( field ), value );
},
/**
* It is also important that our own definitions do not pollute the
* global scope; reasons for this are not just to be polite, but also
* because other code/libraries may provide their own definitions that
* we would not want to interfere with. (Indeed, we'd also want to use
* those definitions, if they already exist before provideAlt is
* called.)
*/
'Providing alternative will not pollute the global scope': function()
{
this.Sut().provideAlt( this.uniq, function() { return {} } );
this.assertEqual( this.gobj[ this.uniq ], undefined );
},
/**
* Our alternatives are unneeded if the object we are providing an
* alternative for is already defined.
*/
'Providing alternative will not modify global if name exists':
function()
{
var sut = this.Sut();
// a field that must exist in ES3+
var field = 'Array',
orig = this.gobj[ field ];
sut.provideAlt( field, function() { return {}; } );
this.assertStrictEqual( sut.get( field ), orig );
},
/**
* Once an alternative is defined, it shall be treated as though the
* value were defined globally; providing additional alternatives should
* therefore have no effect.
*/
'Providing alternative twice will not modify first alternative':
function()
{
var sut = this.Sut();
field = this.uniq,
expected = { _: 'easejsOK' };
// first should provide alternative, second should do nothing
sut.provideAlt( field, function() { return expected; } );
sut.provideAlt( field, function() { return 'oops'; } );
this.assertStrictEqual( sut.get( field ), expected );
},
'provideAlt returns self for method chaining': function()
{
var sut = this.Sut();
this.assertStrictEqual( sut,
sut.provideAlt( 'foo', function() {} )
);
},
} );

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@ -0,0 +1,41 @@
/**
* Tests utility module entry point
*
* Copyright (C) 2014 Free Software Foundation, Inc.
*
* This file is part of GNU ease.js.
*
* ease.js is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* N.B. Despite this saying that it tests the index (i.e. entry point), this
* is not yet the case; it will be in the future, though.
*/
require( 'common' ).testCase(
{
caseSetUp: function()
{
this.Sut = this.require( 'util' );
},
'Exposes Global prototype': function()
{
this.assertStrictEqual(
this.Sut.Global,
this.require( 'util/Global' )
);
},
} );