这句话的意思是 ：
当前窗口的 父窗口（一般会是主框架）下的main窗口的location（即地址栏的地址）；
比如一个页面A是个frameset页面，框架页。
该框架页有两个框架窗口组成。
<frameset rows="126,*" cols="*" framespacing="0" frameborder="no" border="0">
<frame src="timer.php" name="head" scrolling="No" noresize="noresize" id="head">
<frame src="frame2.php" name="main" id="main">
</frameset>
页面A是个frameset页面是parent窗口，该窗口包括
两个框架窗口 分别是 head 窗口 和 main。
head窗口的页面location指向timer.php，那么在timer.php页面parent.main.location ，parent就是frameset 框架窗口，main 窗口的location便是frame2.php。
项目中对应的问题
有一个JS。blackbird.JS 是一个遮罩层。
一开始命名为 var NAMESPACE = 'log';
后来在
window[NAMESPACE] = {
toggle:
function() { (isVisible()) ? hide() : show(); },
定义了其使用方式。
此JS本身是一个对象。（function（）{}）（）
/*
Blackbird - Open Source JavaScript Logging Utility
Author: G Scott Olson
Web: http://blackbirdjs.googlecode.com/
http://www.gscottolson.com/blackbirdjs/
Version: 1.0
The MIT License - Copyright (c) 2008 Blackbird Project
*/
(function() {
var NAMESPACE = 'log';
var IE6_POSITION_FIXED = true; // enable IE6 {position:fixed}
var bbird;
var outputList;
var cache = [];
var state = getState();
var classes = {};
var profiler = {};
var IDs = {
blackbird: 'blackbird',
checkbox: 'bbVis',
filters: 'bbFilters',
controls: 'bbControls',
size: 'bbSize'
}
var messageTypes = { //order of these properties imply render order of filter controls
debug: true,
info: true,
warn: true,
error: true,
profile: true
};
function generateMarkup() { //build markup
var spans = [];
for (type in messageTypes) {
spans.push(['<span class="', type, '" type="', type, '"></span>'].join(''));
}
var newNode = document.createElement('DIV');
newNode.id = IDs.blackbird;
newNode.style.display = 'none';
newNode.innerHTML = [
'<div class="header">',
'<div class="left">',
'<div id="', IDs.filters, '" class="filters" title="点击过滤相应信息">', spans.join(''), '</div>',
'</div>',
'<div class="right">',
'<div id="', IDs.controls, '" class="controls">',
'<span id="', IDs.size, '" title="contract" op="resize"></span>',
'<span class="clear" title="clear" op="clear"></span>',
'<span class="close" title="close" op="close"></span>',
'</div>',
'</div>',
'</div>',
'<div class="main">',
'<div class="left"></div><div class="mainBody">',
'<ol>', cache.join(''), '</ol>',
'</div><div class="right"></div>',
'</div>',
'<div class="footer">',
'<div class="left"><label for="', IDs.checkbox, '"><input type="checkbox" id="', IDs.checkbox, '" />登陆后显示提醒</label></div>',
'<div class="right"></div>',
'</div>'
].join('');
return newNode;
}
function backgroundImage() { //(IE6 only) change <BODY> tag's background to resolve {position:fixed} support
var bodyTag = document.getElementsByTagName('BODY')[0];
if (bodyTag.currentStyle && IE6_POSITION_FIXED) {
if (bodyTag.currentStyle.backgroundImage == 'none') {
bodyTag.style.backgroundImage = 'url(about:blank)';
}
if (bodyTag.currentStyle.backgroundAttachment == 'scroll') {
bodyTag.style.backgroundAttachment = 'fixed';
}
}
}
function addMessage(type, content) { //adds a message to the output list
content = (content.constructor == Array) ? content.join('') : content;
if (outputList) {
var newMsg = document.createElement('LI');
newMsg.className = type;
newMsg.innerHTML = ['<span class="icon"></span>', content].join('');
outputList.appendChild(newMsg);
scrollToBottom();
} else {
cache.push(['<li class="', type, '"><span class="icon"></span>', content, '</li>'].join(''));
}
}
function clear() { //clear list output
outputList.innerHTML = '';
}
function clickControl(evt) {
if (!evt) evt = window.event;
var el = (evt.target) ? evt.target : evt.srcElement;
if (el.tagName == 'SPAN') {
switch (el.getAttributeNode('op').nodeValue) {
case 'resize': resize(); break;
case 'clear': clear(); break;
case 'close': hide(); break;
}
}
}
function clickFilter(evt) { //show/hide a specific message type
if (!evt) evt = window.event;
var span = (evt.target) ? evt.target : evt.srcElement;
if (span && span.tagName == 'SPAN') {
var type = span.getAttributeNode('type').nodeValue;
if (evt.altKey) {
var filters = document.getElementById(IDs.filters).getElementsByTagName('SPAN');
var active = 0;
for (entry in messageTypes) {
if (messageTypes[entry]) active++;
}
var oneActiveFilter = (active == 1 && messageTypes[type]);
for (var i = 0; filters[i]; i++) {
var spanType = filters[i].getAttributeNode('type').nodeValue;
filters[i].className = (oneActiveFilter || (spanType == type)) ? spanType : spanType + 'Disabled';
messageTypes[spanType] = oneActiveFilter || (spanType == type);
}
}
else {
messageTypes[type] = !messageTypes[type];
span.className = (messageTypes[type]) ? type : type + 'Disabled';
}
//build outputList's class from messageTypes object
var disabledTypes = [];
for (type in messageTypes) {
if (!messageTypes[type]) disabledTypes.push(type);
}
disabledTypes.push('');
outputList.className = disabledTypes.join('Hidden ');
scrollToBottom();
}
}
function clickVis(evt) {
if (!evt) evt = window.event;
var el = (evt.target) ? evt.target : evt.srcElement;
state.load = el.checked;
setState();
}
function scrollToBottom() { //scroll list output to the bottom
outputList.scrollTop = outputList.scrollHeight;
}
function isVisible() { //determine the visibility
return (bbird.style.display == 'block');
}
function hide() {
bbird.style.display = 'none';
}
function show() {
var body = document.getElementsByTagName('BODY')[0];
body.removeChild(bbird);
body.appendChild(bbird);
bbird.style.display = 'block';
}
//sets the position
function reposition(position) {
if (position === undefined || position == null) {
position = (state && state.pos === null) ? 1 : (state.pos + 1) % 4; //set to initial position ('topRight') or move to next position
}
switch (position) {
case 0: classes[0] = 'bbTopLeft'; break;
case 1: classes[0] = 'bbTopRight'; break;
case 2: classes[0] = 'bbBottomLeft'; break;
case 3: classes[0] = 'bbBottomRight'; break;
}
state.pos = position;
setState();
}
function resize(size) {
if (size === undefined || size === null) {
size = (state && state.size == null) ? 0 : (state.size + 1) % 2;
}
classes[1] = (size === 0) ? 'bbSmall' : 'bbLarge'
var span = document.getElementById(IDs.size);
span.title = (size === 1) ? 'small' : 'large';
span.className = span.title;
state.size = size;
setState();
scrollToBottom();
}
function setState() {
var props = [];
for (entry in state) {
var value = (state[entry] && state[entry].constructor === String) ? '"' + state[entry] + '"' : state[entry];
props.push(entry + ':' + value);
}
props = props.join(',');
var expiration = new Date();
expiration.setDate(expiration.getDate() + 14);
document.cookie = ['blackbird={', props, '}; expires=', expiration.toUTCString(), ';'].join('');
var newClass = [];
for (word in classes) {
newClass.push(classes[word]);
}
bbird.className = newClass.join(' ');
}
function getState() {
var re = new RegExp(/blackbird=({[^;]+})(;|\b|$)/);
var match = re.exec(document.cookie);
return (match && match[1]) ? eval('(' + match[1] + ')') : { pos: null, size: null, load: null };
}
//event handler for 'keyup' event for window
function readKey(evt) {
if (!evt) evt = window.event;
var code = 113; //F2 key
if (evt && evt.keyCode == code) {
var visible = isVisible();
if (visible && evt.shiftKey && evt.altKey) clear();
else if (visible && evt.shiftKey) reposition();
else if (!evt.shiftKey && !evt.altKey) {
(visible) ? hide() : show();
}
}
}
//event management ( thanks John Resig )
function addEvent(obj, type, fn) {
var obj = (obj.constructor === String) ? document.getElementById(obj) : obj;
if (obj.attachEvent) {
obj['e' + type + fn] = fn;
obj[type + fn] = function() { obj['e' + type + fn](window.event) };
obj.attachEvent('on' + type, obj[type + fn]);
} else obj.addEventListener(type, fn, false);
}
function removeEvent(obj, type, fn) {
var obj = (obj.constructor === String) ? document.getElementById(obj) : obj;
if (obj.detachEvent) {
obj.detachEvent('on' + type, obj[type + fn]);
obj[type + fn] = null;
} else obj.removeEventListener(type, fn, false);
}
window[NAMESPACE] = {
toggle:
function() { (isVisible()) ? hide() : show(); },
resize:
function() { resize(); },
clear:
function() { clear(); },
move:
function() { reposition(); },
debug:
function(msg) { addMessage('debug', msg); },
warn:
function(msg) { addMessage('warn', msg); },
info:
function(msg) { addMessage('info', msg); },
error:
function(msg) { addMessage('error', msg); },
profile:
function(label) {
var currentTime = new Date(); //record the current time when profile() is executed
if (label == undefined || label == '') {
addMessage('error', '<b>ERROR:</b> Please specify a label for your profile statement');
}
else if (profiler[label]) {
addMessage('profile', [label, ': ', currentTime - profiler[label], 'ms'].join(''));
delete profiler[label];
}
else {
profiler[label] = currentTime;
addMessage('profile', label);
}
return currentTime;
}
}
addEvent(window, 'load',
/* initialize Blackbird when the page loads */
function() {
var body = document.getElementsByTagName('BODY')[0];
bbird = body.appendChild(generateMarkup());
outputList = bbird.getElementsByTagName('OL')[0];
backgroundImage();
//add events
addEvent(IDs.checkbox, 'click', clickVis);
addEvent(IDs.filters, 'click', clickFilter);
addEvent(IDs.controls, 'click', clickControl);
addEvent(document, 'keyup', readKey);
resize(state.size);
reposition(state.pos);
if (state.load) {
show();
document.getElementById(IDs.checkbox).checked = true;
}
scrollToBottom();
window[NAMESPACE].init = function() {
show();
window[NAMESPACE].error(['<b>', NAMESPACE, '</b> can only be initialized once']);
}
addEvent(window, 'unload', function() {
removeEvent(IDs.checkbox, 'click', clickVis);
removeEvent(IDs.filters, 'click', clickFilter);
removeEvent(IDs.controls, 'click', clickControl);
removeEvent(document, 'keyup', readKey);
});
});
})();