tinycon.js是一款类似做提示的js库，通过favicon创建提示，不支持的浏览器则用title,其实chrome下有类似的技术Desktop Notification
地址：https://github.com/tommoor/tinycon
附带简单的源码注释：
<html>
<head>
<link rel="icon" href="favicon.ico">
<title>Tinycon</title>
<script>
/*!
* Tinycon - A small library for manipulating the Favicon
* Tom Moor, http://tommoor.com
* Copyright (c) 2012 Tom Moor
* MIT Licensed
* @version 0.5
*/
(function(){
var Tinycon = {};
var currentFavicon = null;
var originalFavicon = null;
var originalTitle = document.title; //原来title，fallback 不支持的浏览器
var faviconImage = null;
var canvas = null;
var options = {};
var defaults = {
7,
height: 9,
font: '10px arial',
colour: '#ffffff',
background: '#F03D25',
fallback: true,
abbreviate: true //使简短；缩简；缩略
};
var ua = (function () { //浏览器嗅探
var agent = navigator.userAgent.toLowerCase();
// New function has access to 'agent' via closure
return function (browser) {
return agent.indexOf(browser) !== -1;
};
}());
var browser = {
ie: ua('msie'),
chrome: ua('chrome'),
webkit: ua('chrome') || ua('safari'),
safari: ua('safari') && !ua('chrome'),
mozilla: ua('mozilla') && !ua('chrome') && !ua('safari')
};
// private methods
var getFaviconTag = function(){ //获取icon标签
var links = document.getElementsByTagName('link');
for(var i=0, len=links.length; i < len; i++) {
if ((links[i].getAttribute('rel') || '').match(/\bicon\b/)) {
return links[i];
}
}
return false;
};
var removeFaviconTag = function(){ //移出icon标签
var links = document.getElementsByTagName('link');
var head = document.getElementsByTagName('head')[0];
for(var i=0, len=links.length; i < len; i++) {
var exists = (typeof(links[i]) !== 'undefined');
if (exists && (links[i].getAttribute('rel') || '').match(/\bicon\b/)) {
head.removeChild(links[i]);
}
}
};
var getCurrentFavicon = function(){ //获取icon标签href
if (!originalFavicon || !currentFavicon) {
var tag = getFaviconTag();
originalFavicon = currentFavicon = tag ? tag.getAttribute('href') : '/favicon.ico';
}
return currentFavicon;
};
var getCanvas = function (){
if (!canvas) {
canvas = document.createElement("canvas");
canvas.width = 16;
canvas.height = 16;
}
return canvas;
};
var setFaviconTag = function(url){
removeFaviconTag();
var link = document.createElement('link');
link.type = 'image/x-icon';
link.rel = 'icon';
link.href = url;
document.getElementsByTagName('head')[0].appendChild(link);
};
var log = function(message){
if (window.console) window.console.log(message);
};
var drawFavicon = function(label, colour) { //画Favicon
// fallback to updating the browser title if unsupported
if (!getCanvas().getContext || browser.ie || browser.safari || options.fallback === 'force') {
return updateTitle(label);
}
var context = getCanvas().getContext("2d");
var colour = colour || '#000000';
var src = getCurrentFavicon();
faviconImage = new Image();
faviconImage.onload = function() {
// clear canvas
context.clearRect(0, 0, 16, 16);
// draw original favicon
context.drawImage(faviconImage, 0, 0, faviconImage.width, faviconImage.height, 0, 0, 16, 16);
// draw bubble over the top
if ((label + '').length > 0) drawBubble(context, label, colour);
// refresh tag in page
refreshFavicon();
};
// allow cross origin resource requests if the image is not a data:uri
// as detailed here: https://github.com/mrdoob/three.js/issues/1305
if (!src.match(/^data/)) {
faviconImage.crossOrigin = 'anonymous';
}
faviconImage.src = src;
};
var updateTitle = function(label) { //不支持的浏览器则显示在title上
if (options.fallback) {
if ((label + '').length > 0) {
document.title = '(' + label + ') ' + originalTitle;
} else {
document.title = originalTitle;
}
}
};
var drawBubble = function(context, label, colour) { //画提示文字
// automatic abbreviation for long (>2 digits) numbers
if (typeof label == 'number' && label > 99 && options.abbreviate) {
label = abbreviateNumber(label);
}
// bubble needs to be larger for double digits
var len = (label + '').length-1;
var width = options.width + (6*len);
var w = 16-width;
var h = 16-options.height;
// webkit seems to render fonts lighter than firefox
context.font = (browser.webkit ? 'bold ' : '') + options.font;
context.fillStyle = options.background;
context.strokeStyle = options.background;
context.lineWidth = 1;
// bubble
context.fillRect(w,h,width-1,options.height);
// rounded left
context.beginPath();
context.moveTo(w-0.5,h+1);
context.lineTo(w-0.5,15);
context.stroke();
// rounded right
context.beginPath();
context.moveTo(15.5,h+1);
context.lineTo(15.5,15);
context.stroke();
// bottom shadow
context.beginPath();
context.strokeStyle = "rgba(0,0,0,0.3)";
context.moveTo(w,16);
context.lineTo(15,16);
context.stroke();
// label
context.fillStyle = options.colour;
context.textAlign = "right";
context.textBaseline = "top";
// unfortunately webkit/mozilla are a pixel different in text positioning
context.fillText(label, 15, browser.mozilla ? 7 : 6);
};
var refreshFavicon = function(){
// check support
if (!getCanvas().getContext) return;
setFaviconTag(getCanvas().toDataURL());
};
var abbreviateNumber = function(label) { //metric 米制的，公制的，十进制的；度量的；距离的 转换单位
var metricPrefixes = [
['G', 1000000000],
['M', 1000000],
['k', 1000]
];
for(var i = 0; i < metricPrefixes.length; ++i) {
if (label >= metricPrefixes[i][1]) {
label = round(label / metricPrefixes[i][1]) + metricPrefixes[i][0];
break;
}
}
return label;
};
var round = function (value, precision) {
var number = new Number(value);
return number.toFixed(precision);
};
// public methods
Tinycon.setOptions = function(custom){
options = {};
for(var key in defaults){
options[key] = custom.hasOwnProperty(key) ? custom[key] : defaults[key];
}
return this;
};
Tinycon.setImage = function(url){
currentFavicon = url;
refreshFavicon();
return this;
};
Tinycon.setBubble = function(label, colour) {
label = label || '';
drawFavicon(label, colour);
return this;
};
Tinycon.reset = function(){
setFaviconTag(originalFavicon);
};
Tinycon.setOptions(defaults);
window.Tinycon = Tinycon;
})();
(function(){
var count = 0;
setInterval(function(){
Tinycon.setBubble(++count);
}, 1000);
})();
</script>
</head>
<body>
</body>
</html>