Yahoo! UI Library > history > history.js (source view)
/**
*
* The Browser History Manager provides the ability to use the
* back/forward navigation buttons in a DHTML application. It also allows
* a DHTML application to be bookmarked in a specific state.
*
* @module history
* @requires yahoo,event
* @namespace YAHOO.util
* @title Browser History Manager
* @experimental
*/
/**
* The History class provides the ability to use the back/forward navigation
* buttons in a DHTML application. It also allows a DHTML application to
* be bookmarked in a specific state.
*
* @class History
* @constructor
*/
YAHOO.util.History = ( function() {
/**
* String identifying which browser we are in.
* Different code is run depending on which browser you are using.
*
* @property _browser
* @type string
* @default "unknown"
* @private
*/
var _browser = "unknown";
/**
* Our hidden IFrame used to store the browsing history.
*
* @property _iframe
* @type HTMLIFrameElement
* @default null
* @private
*/
var _iframe = null;
/**
* INPUT field (with type="hidden" or type="text") or TEXTAREA.
* This field keeps the value of the initial state, current state
* the list of all states across pages within a single browser session.
*
* @property _storageField
* @type HTMLInputElement|HTMLTextAreaElement
* @default null
* @private
*/
var _storageField = null;
/**
* Flag used to tell whether YAHOO.util.History.initialize has been called.
*
* @property _initialized
* @type boolean
* @default false
* @private
*/
var _initialized = false;
/**
* Flag used to tell whether the storage field is ready to be used.
*
* @property _storageFieldReady
* @type boolean
* @default false
* @private
*/
var _storageFieldReady = false;
/**
* Flag used to tell whether the Browser History Manager is ready.
*
* @property _bhmReady
* @type boolean
* @default false
* @private
*/
var _bhmReady = false;
/**
* List of registered modules.
*
* @property _modules
* @type array
* @default []
* @private
*/
var _modules = [];
/**
* List of fully qualified states. This is used only by Safari.
*
* @property _fqstates
* @type array
* @default []
* @private
*/
var _fqstates = [];
/**
* Trims a string.
*
* @method _trim
* @param {string} str The string to be trimmed.
* @return {string} The trimmed string
* @private
*/
function _trim( str ) {
return str.replace( /^\s*(\S*(\s+\S+)*)\s*$/, "$1" );
}
/**
* location.hash is a bit buggy on Opera. I have seen instances where
* navigating the history using the back/forward buttons, and hence
* changing the URL, would not change location.hash. That's ok, the
* implementation of an equivalent is trivial.
*
* @method _getHash
* @return {string} The hash portion of the document's location
* @private
*/
function _getHash() {
var href = top.location.href;
var idx = href.indexOf( "#" );
return idx >= 0 ? href.substr( idx+1 ) : null;
}
/**
* Stores all the registered modules' initial state and current state.
* On Safari, we also store all the fully qualified states visited by
* the application within a single browser session. The storage takes
* place in the form field specified during initialization.
*
* @method _storeStates
* @private
*/
function _storeStates() {
var initialStates = [];
var currentStates = [];
for ( var moduleName in _modules ) {
var moduleObj = _modules[moduleName];
initialStates.push( moduleName + "=" + moduleObj.initialState );
currentStates.push( moduleName + "=" + moduleObj.currentState );
}
_storageField.value = initialStates.join( "&" ) + "|" + currentStates.join( "&" );
if ( _browser == "safari" ) {
_storageField.value += "|" + _fqstates.join( "," );
}
}
/**
* Periodically checks whether our internal IFrame is ready to be used.
*
* @method _checkIframeLoaded
* @private
*/
function _checkIframeLoaded() {
if ( !_iframe.contentWindow || !_iframe.contentWindow.document ) {
// Check again in 10 msec...
setTimeout( _checkIframeLoaded, 10 );
return;
}
// Start the thread that will have the responsibility to
// periodically check whether a navigate operation has been
// requested on the main window. This will happen when
// YAHOO.util.History.navigate has been called or after
// the user has hit the back/forward button.
var doc = _iframe.contentWindow.document;
var elem = doc.getElementById( "state" );
// We must use innerText, and not innerHTML because our string contains
// the "&" character (which would end up being escaped as "&") and
// the string comparison would fail...
var fqstate = elem ? elem.innerText : null;
setInterval( function() {
doc = _iframe.contentWindow.document;
elem = doc.getElementById( "state" );
// See my comment above about using innerText instead of innerHTML...
var newfqstate = elem ? elem.innerText : null;
if ( newfqstate != fqstate ) {
fqstate = newfqstate;
_handleFQStateChange( fqstate );
var hash;
if ( !fqstate ) {
var states = [];
for ( var moduleName in _modules ) {
var moduleObj = _modules[moduleName];
states.push( moduleName + "=" + moduleObj.initialState );
}
hash = states.join( "&" );
} else {
hash = fqstate;
}
// Allow the state to be bookmarked without messing up the browser history...
top.location.replace( "#" + hash );
_storeStates();
}
}, 50 );
_bhmReady = true;
YAHOO.util.History.onLoadEvent.fire();
}
/**
* Sets the new currentState attribute of all modules depending on the new
* fully qualified state. Also notifies the modules which current state has
* changed.
*
* @method _handleFQStateChange
* @param {string} fqstate Fully qualified state
* @private
*/
function _handleFQStateChange( fqstate ) {
var moduleName, moduleObj, currentState;
if ( !fqstate ) {
// Notifies all modules
for ( moduleName in _modules ) {
moduleObj = _modules[moduleName];
moduleObj.currentState = moduleObj.initialState;
moduleObj.onStateChange( moduleObj.currentState );
}
return;
}
var modules = [];
var states = fqstate.split( "&" );
for ( var idx=0, len=states.length ; idx<len ; idx++ ) {
var tokens = states[idx].split( "=" );
if ( tokens.length == 2 ) {
moduleName = tokens[0];
currentState = tokens[1];
modules[moduleName] = currentState;
}
}
for ( moduleName in _modules ) {
moduleObj = _modules[moduleName];
currentState = modules[moduleName];
if ( !currentState || moduleObj.currentState != currentState ) {
moduleObj.currentState = currentState || moduleObj.initialState;
moduleObj.onStateChange( moduleObj.currentState );
}
}
}
/**
* Finish up the initialization of the Browser History Manager.
*
* @method _initialize
* @private
*/
function _initialize() {
_storageField = document.getElementById( "yui_hist_field" );
// Decode the content of our storage field...
var parts = _storageField.value.split( "|" );
if ( parts.length > 1 ) {
var idx, len, tokens, moduleName, moduleObj;
var initialStates = parts[0].split( "&" );
for ( idx=0, len=initialStates.length ; idx<len ; idx++ ) {
tokens = initialStates[idx].split( "=" );
if ( tokens.length == 2 ) {
moduleName = tokens[0];
var initialState = tokens[1];
moduleObj = _modules[moduleName];
if ( moduleObj ) {
moduleObj.initialState = initialState;
}
}
}
var currentStates = parts[1].split( "&" );
for ( idx=0, len=currentStates.length ; idx<len ; idx++ ) {
tokens = currentStates[idx].split( "=" );
if ( tokens.length >= 2 ) {
moduleName = tokens[0];
var currentState = tokens[1];
moduleObj = _modules[moduleName];
if ( moduleObj ) {
moduleObj.currentState = currentState;
}
}
}
}
if ( parts.length > 2 ) {
_fqstates = parts[2].split( "," );
}
_storageFieldReady = true;
if ( _browser == "msie" ) {
_iframe = document.getElementById( "yui_hist_iframe" );
_checkIframeLoaded();
} else {
// Start the thread that will have the responsibility to
// periodically check whether a navigate operation has been
// requested on the main window. This will happen when
// YAHOO.util.History.navigate has been called or after
// the user has hit the back/forward button.
// On Safari 1.x and 2.0, the only way to catch a back/forward
// operation is to watch history.length... We basically exploit
// what I consider to be a bug (history.length is not supposed
// to change when going back/forward in the history...) This is
// why, in the following thread, we first compare the hash,
// because the hash thing will be fixed in the next major
// version of Safari. So even if they fix the history.length
// bug, all this will still work!
var counter = history.length;
// On Gecko and Opera, we just need to watch the hash...
var hash = _getHash();
setInterval( function() {
var state;
var newHash = _getHash();
var newCounter = history.length;
if ( newHash != hash ) {
hash = newHash;
counter = newCounter;
_handleFQStateChange( hash );
_storeStates();
} else if ( newCounter != counter ) {
// If we ever get here, we should be on Safari...
hash = newHash;
counter = newCounter;
state = _fqstates[counter-1];
_handleFQStateChange( state );
_storeStates();
}
}, 50 );
_bhmReady = true;
YAHOO.util.History.onLoadEvent.fire();
}
}
// Simple browser detection code
// After talking with Matt Sweeney, I moved back to using the
// user agent string instead of doing browser detection.
var ua = navigator.userAgent.toLowerCase();
if ( ua.indexOf( "opera" ) != -1 ) {
// Opera (check first in case of spoof)
_browser = "opera";
} else if ( ua.indexOf( "msie" ) != -1 ) {
// Microsoft Internet Explorer and derivatives...
_browser = "msie";
} else if ( ua.indexOf( "safari" ) != -1 ) {
// Safari (check before Gecko because it includes "like Gecko")
_browser = "safari";
} else if ( ua.indexOf( "gecko" ) != -1 ) {
// Gecko
_browser = "gecko";
}
return {
/**
* Fired when the Browser History Manager is ready.
*
* @event onLoadEvent
*/
onLoadEvent : new YAHOO.util.CustomEvent( "onLoad" ),
/**
* Registers a new module.
*
* @method register
* @param {string} module Non-empty string uniquely identifying the
* module you wish to register.
* @param {string} initialState The initial state of the specified
* module corresponding to its earliest history entry.
* @param {function} onStateChange Callback called when the
* state of the specified module has changed.
*/
register : function( module, initialState, onStateChange ) {
if ( typeof module != "string" || _trim( module ) === "" ||
typeof initialState != "string" ||
typeof onStateChange != "function" ) {
throw new Error( "Missing or invalid argument passed to YAHOO.util.History.register" );
}
if ( _modules[module] ) {
throw new Error( "A module cannot be registered twice" );
}
// Note: A module CANNOT be registered after calling
// YAHOO.util.History.initialize. Indeed, we set the initial state
// of each registered module in YAHOO.util.History.initialize.
// If you could register a module after initializing the Browser
// History Manager, you would not read the correct state using
// YAHOO.util.History.getCurrentState when coming back to the
// page using the back button.
if ( _initialized ) {
throw new Error( "All modules must be registered before calling YAHOO.util.History.initialize" );
}
// Make sure the strings passed in do not contain our separators "," and "|"
module = escape( module );
initialState = escape( initialState );
_modules[module] = {
name : module,
initialState : initialState,
currentState : initialState,
onStateChange : onStateChange
};
},
/**
* Initializes the Browser History Manager. Call this method
* from a script block located right after the opening body tag.
*
* @method initialize
* @param {string} iframeTarget Optional - Path to an existing
* HTML document accessible from the same domain. If not
* specified, defaults to "blank.html"
* @public
*/
initialize : function( iframeTarget ) {
// Return if the browser history manager has already been initialized
if ( _initialized ) {
return;
}
if ( _browser == "unknown" ) {
throw new Error( "Your web browser is not supported by the Browser History Manager" );
}
if ( !iframeTarget ) {
iframeTarget = "blank.html";
}
if ( typeof iframeTarget != "string" || _trim( iframeTarget ) === "" ) {
throw new Error( "Invalid argument passed to YAHOO.util.History.initialize" );
}
document.write( '<input type="hidden" id="yui_hist_field">' );
if ( _browser == "msie" ) {
// Pointing the IFrame to a file on the server is absolutely
// essential. I tried to point it to nothing (by setting
// src="") and create the initial entry in the browser
// history (by using document.write) but it did not work
// when coming back to the page... Also, the file must exist
// on the server!
document.write( '<iframe id="yui_hist_iframe" src="' + iframeTarget + '" style="position:absolute;visibility:hidden;"></iframe>' );
}
// We have to wait for the window's onload handler. Otherwise, our
// hidden form field will always be empty (i.e. the browser won't
// have had enough time to restore the session)
YAHOO.util.Event.addListener( window, "load", _initialize );
_initialized = true;
},
/**
* Call this method when you want to store a new entry in the browser's history.
*
* @method navigate
* @param {string} module Non-empty string representing your module.
* @param {string} state String representing the new state of the specified module.
* @return {boolean} Indicates whether the new state was successfully added to the history.
* @public
*/
navigate : function( module, state ) {
if ( typeof module != "string" || typeof state != "string" ) {
throw new Error( "Missing or invalid argument passed to YAHOO.util.History.navigate" );
}
if ( !_bhmReady ) {
throw new Error( "The Browser History Manager is not initialized" );
}
if ( !_modules[module] ) {
throw new Error( "The following module has not been registered: " + module );
}
// Make sure the strings passed in do not contain our separators "," and "|"
module = escape( module );
state = escape( state );
// Generate our new full state string mod1=xxx&mod2=yyy
var currentStates = [];
for ( var moduleName in _modules ) {
var moduleObj = _modules[moduleName];
var currentState = ( moduleName == module ) ? state : moduleObj.currentState;
currentStates.push( moduleName + "=" + currentState );
}
var fqstate = currentStates.join( "&" );
if ( _browser == "msie" ) {
// Add a new entry to the browser's history...
var html = '<html><body><div id="state">' + fqstate + '</div></body></html>';
try {
var doc = _iframe.contentWindow.document;
doc.open();
doc.write( html );
doc.close();
} catch ( e ) {
return false;
}
} else {
// Known bug: On Safari 1.x and 2.0, if you have tab browsing
// enabled, Safari will show an endless loading icon in the
// tab. This has apparently been fixed in recent WebKit builds.
// One work around found by Dav Glass is to submit a form that
// points to the same document. This indeed works on Safari 1.x
// and 2.0 but creates bigger problems on WebKit. So for now,
// we'll consider this an acceptable bug, and hope that Apple
// comes out with their next version of Safari very soon.
top.location.hash = fqstate;
if ( _browser == "safari" ) {
// The following two lines are only useful for Safari 1.x
// and 2.0. Recent nightly builds of WebKit do not require
// that, but unfortunately, it is not easy to differentiate
// between the two. Once Safari 2.0 departs the A-grade
// list, we can remove the following two lines...
_fqstates[history.length] = fqstate;
_storeStates();
}
}
return true;
},
/**
* Returns the current state of the specified module.
*
* @method getCurrentState
* @param {string} module Non-empty string representing your module.
* @return {string} The current state of the specified module.
* @public
*/
getCurrentState : function( module ) {
if ( typeof module != "string" ) {
throw new Error( "Missing or invalid argument passed to YAHOO.util.History.getCurrentState" );
}
if ( !_storageFieldReady ) {
throw new Error( "The Browser History Manager is not initialized" );
}
var moduleObj = _modules[module];
if ( !moduleObj ) {
throw new Error( "No such registered module: " + module );
}
return unescape( moduleObj.currentState );
},
/**
* Returns the state of a module according to the URL fragment
* identifier. This method is useful to initialize your modules
* if your application was bookmarked from a particular state.
*
* @method getBookmarkedState
* @param {string} module Non-empty string representing your module.
* @return {string} The bookmarked state of the specified module.
* @public
*/
getBookmarkedState : function( module ) {
if ( typeof module != "string" ) {
throw new Error( "Missing or invalid argument passed to YAHOO.util.History.getBookmarkedState" );
}
var hash = top.location.hash.substr(1);
var states = hash.split( "&" );
for ( var idx=0, len=states.length ; idx<len ; idx++ ) {
var tokens = states[idx].split( "=" );
if ( tokens.length == 2 ) {
var moduleName = tokens[0];
if ( moduleName == module ) {
return tokens[1];
}
}
}
return null;
},
/**
* Returns the value of the specified query string parameter.
* This method is not used internally by the Browser History Manager.
* However, it is provided here as a helper since many applications
* using the Browser History Manager will want to read the value of
* url parameters to initialize themselves.
*
* @method getQueryStringParameter
* @param {string} paramName Name of the parameter we want to look up.
* @param {string} queryString Optional URL to look at. If not specified,
* this method uses the URL in the address bar.
* @return {string} The value of the specified parameter, or null.
* @public
*/
getQueryStringParameter : function( paramName, url ) {
url = url || top.location.href;
var idx = url.indexOf( "?" );
var queryString = idx >= 0 ? url.substr( idx+1 ) : url;
var params = queryString.split( "&" );
for ( var i=0, len=params.length ; i<len ; i++ ) {
var tokens = params[i].split( "=" );
if ( tokens.length >= 2 ) {
if ( tokens[0] == paramName ) {
return tokens[1];
}
}
}
return null;
}
};
} )();