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easejs/lib/util.js

608 lines
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JavaScript

/**
* Contains utilities functions shared by modules
*
* Copyright (C) 2010 Mike Gerwitz
*
* This file is part of ease.js.
*
* ease.js 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.
*
* 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 Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @author Mike Gerwitz
*/
var propParseKeywords = require( __dirname + '/prop_parser' ).parseKeywords;
/**
* Whether we can actually define properties, or we need to fall back
*
* This check actually attempts to set a property and fails if there's an error.
* This is needed because IE8 has a broken implementation, yet still defines
* Object.defineProperty for use with DOM elements. Just another day in the life
* of a web developer.
*
* This test is only performed once, when the module is first loaded. Don't
* expect a performance hit from it.
*
* @type {boolean}
*/
var can_define_prop = ( function()
{
if ( typeof Object.defineProperty === 'function' )
{
try
{
// perform test, primarily for IE8
Object.defineProperty( {}, 'x', {} );
return true;
}
catch ( e ) {}
}
return false;
} )();
/**
* Freezes an object if freezing is supported
*
* @param {Object} obj object to freeze
*
* @return {Object} object passed to function
*/
exports.freeze = ( typeof Object.freeze === 'function' )
? Object.freeze
: function( obj )
{
return;
}
;
/**
* Gets/sets whether the system needs to fall back to defining properties in a
* normal manner when use of Object.defineProperty() is requested
*
* This will be set by default if the JS engine does not support the
* Object.defineProperty method from ECMAScript 5.
*
* @param {boolean=} val value, if used as setter
*
* @return {boolean|Object} current value if getter, self if setter
*/
exports.definePropertyFallback = function( val )
{
if ( val === undefined )
{
return !can_define_prop;
}
can_define_prop = !val;
exports.defineSecureProp = getDefineSecureProp();
return exports;
};
/**
* Attempts to define a non-enumerable, non-writable and non-configurable
* property on the given object
*
* If the operation is unsupported, a normal property will be set.
*
* @param {Object} obj object to set property on
* @param {string} prop name of property to set
* @param {*} value value to set
*
* @return {undefined}
*/
exports.defineSecureProp = getDefineSecureProp();
/**
* Clones an object
*
* @param {*} data object to clone
* @param {boolean=} deep perform deep clone (defaults to shallow)
*
* @return {*} cloned object
*
* Closure Compiler ignores typeof checks and is thusly confused:
* @suppress {checkTypes}
*/
exports.clone = function clone( data, deep )
{
deep = !!deep;
if ( data instanceof Array )
{
if ( !deep )
{
// return a copy of the array
return data.slice( 0 );
}
// if we're performing a deep clone, we have to loop through each of the
// elements of the array and clone them
var ret = [];
for ( var i = 0, len = data.length; i < len; i++ )
{
// clone this element
ret.push( clone( data[ i ], deep ) );
}
return ret;
}
else if ( typeof data === 'function' )
{
// It is pointless to clone a function. Even if we did clone those that
// support toSource(), they'd still do the same damn thing.
return data;
}
// explicitly testing with instanceof will ensure we're actually testing an
// object, not something that may be misinterpreted as one (e.g. null)
else if ( data instanceof Object )
{
var newobj = {},
hasOwn = Object.prototype.hasOwnProperty;
// copy data to the new object
for ( var prop in data )
{
if ( hasOwn.call( data, prop ) )
{
newobj[ prop ] = ( deep )
? clone( data[ prop ] )
: data[ prop ]
;
}
}
return newobj;
}
// primitive type; cloning unnecessary
return data;
};
/**
* Copies properties from one object to another
*
* This method is designed to support very basic object extensions. The
* destination argument is first to allow extending an object without using the
* full-blown class system.
*
* If a deep copy is not performed, all values will be copied by reference.
*
* @param {Object} dest destination object
* @param {Object} src source object
* @param {boolean} deep perform deep copy (slower)
*
* @return {Object} dest
*/
exports.copyTo = function( dest, src, deep )
{
deep = !!deep;
var get, set, data;
// sanity check
if ( !( dest instanceof Object ) || !( src instanceof Object ) )
{
throw TypeError(
"Must provide both source and destination objects"
);
}
// slower; supports getters/setters
if ( can_define_prop )
{
for ( var prop in src )
{
data = Object.getOwnPropertyDescriptor( src, prop );
if ( data.get || data.set )
{
// Define the property the slower way (only needed for
// getters/setters). We don't have to worry about cloning in
// this case, since getters/setters are methods.
Object.defineProperty( dest, prop, data );
}
else
{
// normal copy; cloned if deep, otherwise by reference
dest[ prop ] = ( deep )
? exports.clone( src[ prop ], true )
: src[ prop ]
;
}
}
}
// quick (keep if statement out of the loop)
else
{
for ( var prop in src )
{
// normal copy; cloned if deep, otherwise by reference
dest[ prop ] = ( deep )
? exports.clone( src[ prop ], true )
: src[ prop ]
;
}
}
// return dest for convenience (and to feel useful about ourselves)
return dest;
};
/**
* Parses object properties to determine how they should be interpreted in an
* Object Oriented manner
*
* @param {!Object} data properties with names as the key
*
* @param {!{each,property,method,getset,keywordParser}} options
* parser options and callbacks
*
* @return undefined
*/
exports.propParse = function( data, options )
{
// todo: profile; function calls are more expensive than if statements, so
// it's probably a better idea not to use fvoid
var fvoid = function() {},
callbackEach = options.each || undefined,
callbackProp = options.property || fvoid,
callbackMethod = options.method || fvoid,
callbackGetSet = options.getset || fvoid,
keywordParser = options.keywordParser || propParseKeywords,
hasOwn = Object.prototype.hasOwnProperty,
parse_data = {},
name = '',
keywords = {},
value = null,
getter = false,
setter = false;
// for each of the given properties, determine what type of property we're
// dealing with (in the classic OO sense)
for ( var prop in data )
{
// ignore properties of instance prototypes
if ( !( hasOwn.call( data, prop ) ) )
{
continue;
}
// retrieve getters/setters, if supported
if ( can_define_prop )
{
var prop_desc = Object.getOwnPropertyDescriptor( data, prop );
getter = prop_desc.get;
setter = prop_desc.set;
}
value = data[ prop ];
parse_data = keywordParser( prop ) || {};
name = parse_data.name || prop;
keywords = parse_data.keywords || {};
if ( options.assumeAbstract || keywords[ 'abstract' ] )
{
// may not be set if assumeAbstract is given
keywords[ 'abstract' ] = true;
if ( !( value instanceof Array ) )
{
throw TypeError(
"Missing parameter list for abstract method: " + name
);
}
verifyAbstractNames( name, value );
value = exports.createAbstractMethod.apply( this, value );
}
// if an 'each' callback was provided, pass the data before parsing it
if ( callbackEach )
{
callbackEach.call( callbackEach, name, value, keywords );
}
// getter/setter
if ( getter || setter )
{
callbackGetSet.call( callbackGetSet,
name, getter, setter, keywords
);
}
// method
else if ( typeof value === 'function' )
{
callbackMethod.call(
callbackMethod,
name,
value,
exports.isAbstractMethod( value ),
keywords
);
}
// simple property
else
{
callbackProp.call( callbackProp, name, value, keywords );
}
}
};
/**
* Only permit valid names for parameter list
*
* In the future, we may add additional functionality, so it's important to
* restrict this as much as possible for the time being.
*
* @param {string} name name of abstract member (for error)
* @param {Object} params parameter list to check
*
* @return {undefined}
*/
function verifyAbstractNames( name, params )
{
var i = params.length;
while ( i-- )
{
if ( params[ i ].match( /^[a-z_][a-z0-9_]*$/i ) === null )
{
throw SyntaxError(
"Member " + name + " contains invalid parameter '" +
params[ i ] + "'"
);
}
}
}
/**
* Creates an abstract method
*
* Abstract methods must be implemented by a subclass and cannot be called
* directly. If a class contains a single abstract method, the class itself is
* considered to be abstract and cannot be instantiated. It may only be
* extended.
*
* @param {...string} def function definition that concrete
* implementations must follow
*
* @return {function()}
*/
exports.createAbstractMethod = function( def )
{
var definition = Array.prototype.slice.call( arguments );
var method = function()
{
throw new Error( "Cannot call abstract method" );
};
exports.defineSecureProp( method, 'abstractFlag', true );
exports.defineSecureProp( method, 'definition', definition );
exports.defineSecureProp( method, '__length', arguments.length );
return method;
};
/**
* Determines if the given function is an abstract method
*
* @param {function()} func function to inspect
*
* @return {boolean} true if function is an abstract method, otherwise false
*
* @suppress {checkTypes}
*/
exports.isAbstractMethod = function( func )
{
return ( ( typeof func === 'function') && ( func.abstractFlag === true ) )
? true
: false
;
};
/**
* Shrinks an array, removing undefined elements
*
* Pushes all items onto a new array, removing undefined elements. This ensures
* that the length of the array represents correctly the number of elements in
* the array.
*
* @param {Array} items array to shrink
*
* @return {Array} shrunken array
*/
exports.arrayShrink = function( items )
{
// copy the methods into a new array by pushing them onto it, to ensure
// the length property of the array will work properly
var arr_new = [];
for ( var i = 0, len = items.length; i < len; i++ )
{
var item = items[ i ];
if ( item === undefined )
{
continue;
}
arr_new.push( item );
}
return arr_new;
};
/**
* Uses Object.getOwnPropertyDescriptor if available, otherwise provides our own
* implementation to fall back on
*/
exports.getOwnPropertyDescriptor =
( can_define_prop && Object.getOwnPropertyDescriptor ) ||
/**
* If the environment does not support retrieving property descriptors
* (ES5), then the following will be true:
* - get/set will always be undefined
* - writable, enumerable and configurable will always be true
* - value will be the value of the requested property on the given object
*
* @param {!Object} obj object to check property on
* @param {string} prop property to retrieve descriptor for
*
* @return {Object|undefined} descriptor for requested property, if found
*/
function( obj, prop )
{
if ( !Object.prototype.hasOwnProperty.call( obj, prop ) )
{
return undefined;
}
// fallback response
return {
get: undefined,
set: undefined,
writable: true,
enumerable: true,
configurable: true,
value: obj[ prop ],
};
};
/**
* Returns prototype of object, or undefined if unsupported
*/
exports.getPrototypeOf = Object.getPrototypeOf || function()
{
return undefined;
};
/**
* Travels down the prototype chain of the given object in search of the
* requested property and returns its descriptor
*
* This operates as Object.getOwnPropertyDescriptor(), except that it traverses
* the prototype chain. For environments that do not support __proto__, it will
* not traverse the prototype chain and essentially serve as an alias for
* getOwnPropertyDescriptor().
*
* This method has the option to ignore the base prototype. This is useful to,
* for example, not catch properties like Object.prototype.toString() when
* searching for 'toString' on an object.
*
* @param {Object} obj object to check property on
* @param {string} prop property to retrieve descriptor for
* @param {boolean} nobase whether to ignore the base prototype
*
* @return {Object} descriptor for requested property or undefined if not found
*/
exports.getPropertyDescriptor = function( obj, prop, nobase )
{
// false by default
nobase = !!nobase;
// note that this uses util's function, not Object's
var desc = exports.getOwnPropertyDescriptor( obj, prop ),
next = exports.getPrototypeOf( obj );
// if we didn't find a descriptor and a prototype is available, recurse down
// the prototype chain, ensuring that the next prototype has a prototype if
// the base is to be excluded
if ( !desc && next && ( !nobase || exports.getPrototypeOf( next ) ) )
{
return exports.getPropertyDescriptor( next, prop, nobase );
}
// return the descriptor or undefined if no prototype is available
return desc;
};
/**
* Indicates whether or not the getPropertyDescriptor method is capable of
* traversing the prototype chain
*
* @type {boolean}
*/
exports.defineSecureProp( exports.getPropertyDescriptor, 'canTraverse',
( Object.getPrototypeOf ) ? true : false
);
/**
* Appropriately returns defineSecureProp implementation to avoid check on each
* invocation
*
* @return {function( Object, string, * )}
*/
function getDefineSecureProp()
{
// falls back to simply defining a normal property
var fallback = function( obj, prop, value )
{
obj[ prop ] = value;
};
if ( !can_define_prop )
{
return fallback;
}
else
{
// uses ECMAScript 5's Object.defineProperty() method
return function( obj, prop, value )
{
try
{
Object.defineProperty( obj, prop,
{
value: value,
enumerable: false,
writable: false,
configurable: false,
});
}
catch ( e )
{
// let's not have this happen again, as repeatedly throwing
// exceptions will do nothing but slow down the system
exports.definePropertyFallback( true );
// if there's an error (ehem, IE8), fall back
fallback( obj, prop, value );
}
};
}
}