HTML5计时器实现方法

高洛峰原创: 2017-03-12 17:03:354299浏览

听到计时器之后或许大家认为只有在js中可以实现，其实这种想法在你不知道有html5的情况下还能成立，下文为大家介绍下html5中是如何实现计时器的，感兴趣的朋友不要错过

html:

<!DOCTYPE html> 
<html> 
<head> 
<meta charset="utf-8"> 
<!-- Always force latest IE rendering engine (even in intranet) & Chrome Frame 
Remove this if you use the .htaccess --> 
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> 
<title>HTML5 Timer for work-relax balance</title> 
<meta name="description" content=""> 
<meta name="author" content="kevin"> 
<meta name="viewport" content="width=device-width; initial-scale=1.0"> 
<!-- Replace favicon.ico & apple-touch-icon.png in the root of your domain and delete these references --> 
<link rel="shortcut icon" href="/favicon.ico"/> 
<link rel="apple-touch-icon" href="/apple-touch-icon.png"/> 
<link rel="stylesheet" type="text/css" href="css/style.css"> 
<script> 
countDownSeconds = 60; 
var handle = null; 
//window load 
function onLoadWindow() { 
aCanvas = document.getElementById("countdownCanvas"); 
context = aCanvas.getContext("2d"); 
var canvasText = "Press to Start..."; 
var xPos = aCanvas.width / 2; 
var yPos = aCanvas.height / 2; 
context.font = "12pt Century Gothic"; 
context.fillStyle = "#008000;"; 
context.textAlign = "center"; 
context.textBaseline = "middle"; 
context.fillText(canvasText, xPos, yPos); 
} 
function updateCanvas(theContext, width, height) { 
if (countDownSeconds < 0) { 
clearInterval(handle); 
handle = null; 
alert("hey, time is up!"); 
return 0; 
} 
minStr = Math.floor(countDownSeconds / 60); 
secStr = countDownSeconds % 60; 
if (minStr < 10) { 
minStr = "0" + minStr; 
} 
if (secStr < 10) { 
secStr = "0" + secStr; 
} 
context.clearRect(0, 0, width, height); 
context.font = "24pt Century Gothic"; 
context.fillText(minStr + " : " + secStr, width / 2, height / 2); 
countDownSeconds--; 
} 
function startWorkCountDown() { 
if (handle != null) { 
clearInterval(handle); 
} 
countDownSeconds = document.getElementById("workIntervalInput").value * 60; 
timeDisplayCanvas = document.getElementById("countdownCanvas"); 
timeDisplayContext2D = timeDisplayCanvas.getContext("2d"); 
updateCanvas(timeDisplayContext2D, timeDisplayCanvas.width, timeDisplayCanvas.height); 
handle = setInterval(function() { 
updateCanvas(timeDisplayContext2D, timeDisplayCanvas.width, timeDisplayCanvas.height); 
}, 1000); 
} 
function startRestCountDown() { 
if (handle != null) { 
clearInterval(handle); 
} 
countDownSeconds = document.getElementById("restIntervalInput").value * 60; 
timeDisplayCanvas = document.getElementById("countdownCanvas"); 
timeDisplayContext2D = timeDisplayCanvas.getContext("2d"); 
updateCanvas(timeDisplayContext2D, timeDisplayCanvas.width, timeDisplayCanvas.height); 
handle = setInterval(function() { 
updateCanvas(timeDisplayContext2D, timeDisplayCanvas.width, timeDisplayCanvas.height); 
}, 1000); 
} 
</script> 
</head> 
<body onload="onLoadWindow()"> 
<p> 
<header> 
<h1>work-life balance timer</h1> 
</header> 
Please choose the work interval: 
<input name="workIntervalInput" id="workIntervalInput" type="number" value="25" min="15" max="45" step="5"/> 
minutes 

Please choose the rest interval: 
<input name="restIntervalInput" id="restIntervalInput" type="number" value="5" min="3" max="10" step="1"/> 
minutes 


<canvas id="countdownCanvas" width="300" height="50" style="border:2px solid black"> 
This is a canvas 
</canvas> 


<button onclick="startWorkCountDown()"> 
Work Hard 
</button> 
<button onclick="startRestCountDown()"> 
Take A Break 
</button> 
<footer> 
<p> 
&copy; Copyright Reserved 
</p> 
</footer> 
</p> 
</body> 
</html>

css3:

/* 
* HTML5 ✰ Boilerplate 
* 
* What follows is the result of much research on cross-browser styling. 
* Credit left inline and big thanks to Nicolas Gallagher, Jonathan Neal, 
* Kroc Camen, and the H5BP dev community and team. 
* 
* Detailed information about this CSS: h5bp.com/css 
* 
* ==|== normalize ========================================================== 
*/ 

/* ============================================================================= 
HTML5 display definitions 
========================================================================== */ 
article, aside, details, figcaption, figure, footer, header, hgroup, nav, section { display: block; } 
header {text-shadow: #220000 0px 0px 10px 10px;} 
audio, canvas, video { display: inline-block; *display: inline; *zoom: 1; } 
audio:not([controls]) { display: none; } 
[hidden] { display: none; } 
/* ============================================================================= 
Base 
========================================================================== */ 
/* 
* 1. Correct text resizing oddly in IE6/7 when body font-size is set using em units 
* 2. Force vertical scrollbar in non-IE 
* 3. Prevent iOS text size adjust on device orientation change, without disabling user zoom: h5bp.com/g 
*/ 
html { font-size: 100%; overflow-y: scroll; -webkit-text-size-adjust: 100%; -ms-text-size-adjust: 100%; } 
body { margin: 0; font-size: 24px; line-height: 1.231;} 
body, button, input, select, textarea {font-family:"Century Gothic"; color:#008000} 
/* 
* Remove text-shadow in selection highlight: h5bp.com/i 
* These selection declarations have to be separate 
* Also: hot pink! (or customize the background color to match your design) 
*/ 
::-moz-selection { background: #fe57a1; color: #fff; text-shadow: none; } 
::selection { background: #fe57a1; color: #fff; text-shadow: none; } 

/* ============================================================================= 
Links 
========================================================================== */ 
a { color: #00e; } 
a:visited { color: #551a8b; } 
a:hover { color: #06e; } 
a:focus { outline: thin dotted; } 
/* Improve readability when focused and hovered in all browsers: h5bp.com/h */ 
a:hover, a:active { outline: 0; } 

/* ============================================================================= 
Typography 
========================================================================== */ 
abbr[title] { border-bottom: 1px dotted; } 
b, strong { font-weight: bold; } 
blockquote { margin: 1em 40px; } 
dfn { font-style: italic; } 
hr { display: block; height: 1px; border: 0; border-top: 1px solid #ccc; margin: 1em 0; padding: 0; } 
ins { background: #ff9; color: #000; text-decoration: none; } 
mark { background: #ff0; color: #000; font-style: italic; font-weight: bold; } 
/* Redeclare monospace font family: h5bp.com/j */ 
pre, code, kbd, samp { font-family: monospace, monospace; _font-family: &#39;courier new&#39;, monospace; font-size: 1em; } 
/* Improve readability of pre-formatted text in all browsers */ 
pre { white-space: pre; white-space: pre-wrap; word-wrap: break-word; } 
q { quotes: none; } 
q:before, q:after { content: ""; content: none; } 
small { font-size: 85%; } 
/* Position subscript and superscript content without affecting line-height: h5bp.com/k */ 
sub, sup { font-size: 75%; line-height: 0; position: relative; vertical-align: baseline; } 
sup { top: -0.5em; } 
sub { bottom: -0.25em; } 

/* ============================================================================= 
Lists 
========================================================================== */ 
ul, ol { margin: 1em 0; padding: 0 0 0 40px; } 
dd { margin: 0 0 0 40px; } 
nav ul, nav ol { list-style: none; list-style-image: none; margin: 0; padding: 0; } 

/* ============================================================================= 
Embedded content 
========================================================================== */ 
/* 
* 1. Improve image quality when scaled in IE7: h5bp.com/d 
* 2. Remove the gap between images and borders on image containers: h5bp.com/e 
*/ 
img { border: 0; -ms-interpolation-mode: bicubic; vertical-align: middle; } 
/* 
* Correct overflow not hidden in IE9 
*/ 
svg:not(:root) { overflow: hidden; } 

/* ============================================================================= 
Figures 
========================================================================== */ 
figure { margin: 0; } 

/* ============================================================================= 
Forms 
========================================================================== */ 
form { margin: 0; } 
fieldset { border: 0; margin: 0; padding: 0; } 
/* Indicate that &#39;label&#39; will shift focus to the associated form element */ 
label { cursor: pointer; } 
/* 
* 1. Correct color not inheriting in IE6/7/8/9 
* 2. Correct alignment displayed oddly in IE6/7 
*/ 
legend { border: 0; *margin-left: -7px; padding: 0; } 
/* 
* 1. Correct font-size not inheriting in all browsers 
* 2. Remove margins in FF3/4 S5 Chrome 
* 3. Define consistent vertical alignment display in all browsers 
*/ 
button, input, select, textarea { font-size: 100%; margin: 0; vertical-align: baseline; *vertical-align: middle; } 
/* 
* 1. Define line-height as normal to match FF3/4 (set using !important in the UA stylesheet) 
* 2. Correct inner spacing displayed oddly in IE6/7 
*/ 
button, input { line-height: normal; *overflow: visible; } 
/* 
* Reintroduce inner spacing in &#39;table&#39; to avoid overlap and whitespace issues in IE6/7 
*/ 
table button, table input { *overflow: auto; } 
/* 
* 1. Display hand cursor for clickable form elements 
* 2. Allow styling of clickable form elements in iOS 
*/ 
button, input[type="button"], input[type="reset"], input[type="submit"] { cursor: pointer; -webkit-appearance: button; } 
/* 
* Consistent box sizing and appearance 
*/ 
input[type="checkbox"], input[type="radio"] { box-sizing: border-box; } 
input[type="search"] { -webkit-appearance: textfield; -moz-box-sizing: content-box; -webkit-box-sizing: content-box; box-sizing: content-box; } 
input[type="search"]::-webkit-search-decoration { -webkit-appearance: none; } 
/* 
* Remove inner padding and border in FF3/4: h5bp.com/l 
*/ 
button::-moz-focus-inner, input::-moz-focus-inner { border: 0; padding: 0; } 
/* 
* 1. Remove default vertical scrollbar in IE6/7/8/9 
* 2. Allow only vertical resizing 
*/ 
textarea { overflow: auto; vertical-align: top; resize: vertical; } 
/* Colors for form validity */ 
input:valid, textarea:valid { } 
input:invalid, textarea:invalid { background-color: #f0dddd; } 

/* ============================================================================= 
Tables 
========================================================================== */ 
table { border-collapse: collapse; border-spacing: 0; } 
td { vertical-align: top; } 

/* ==|== primary styles ===================================================== 
Author: 
========================================================================== */ 

/* ==|== non-semantic helper classes ======================================== 
Please define your styles before this section. 
========================================================================== */ 
/* For image replacement */ 
.ir { display: block; border: 0; text-indent: -999em; overflow: hidden; background-color: transparent; background-repeat: no-repeat; text-align: left; direction: ltr; } 
.ir br { display: none; } 
/* Hide from both screenreaders and browsers: h5bp.com/u */ 
.hidden { display: none !important; visibility: hidden; } 
/* Hide only visually, but have it available for screenreaders: h5bp.com/v */ 
.visuallyhidden { border: 0; clip: rect(0 0 0 0); height: 1px; margin: -1px; overflow: hidden; padding: 0; position: absolute; width: 1px; } 
/* Extends the .visuallyhidden class to allow the element to be focusable when navigated to via the keyboard: h5bp.com/p */ 
.visuallyhidden.focusable:active, .visuallyhidden.focusable:focus { clip: auto; height: auto; margin: 0; overflow: visible; position: static; width: auto; } 
/* Hide visually and from screenreaders, but maintain layout */ 
.invisible { visibility: hidden; } 
/* Contain floats: h5bp.com/q */ 
.clearfix:before, .clearfix:after { content: ""; display: table; } 
.clearfix:after { clear: both; } 
.clearfix { zoom: 1; } 

/* ==|== media queries ====================================================== 
PLACEHOLDER Media Queries for Responsive Design. 
These override the primary (&#39;mobile first&#39;) styles 
Modify as content requires. 
========================================================================== */ 
@media only screen and (min-width: 480px) { 
/* Style adjustments for viewports 480px and over go here */ 
} 
@media only screen and (min-width: 768px) { 
/* Style adjustments for viewports 768px and over go here */ 
} 

/* ==|== print styles ======================================================= 
Print styles. 
Inlined to avoid required HTTP connection: h5bp.com/r 
========================================================================== */ 
@media print { 
* { background: transparent !important; color: black !important; text-shadow: none !important; filter:none !important; -ms-filter: none !important; } /* Black prints faster: h5bp.com/s */ 
a, a:visited { text-decoration: underline; } 
a[href]:after { content: " (" attr(href) ")"; } 
abbr[title]:after { content: " (" attr(title) ")"; } 
.ir a:after, a[href^="javascript:"]:after, a[href^="#"]:after { content: ""; } /* Don&#39;t show links for images, or javascript/internal links */ 
pre, blockquote { border: 1px solid #999; page-break-inside: avoid; } 
thead { display: table-header-group; } /* h5bp.com/t */ 
tr, img { page-break-inside: avoid; } 
img { max-width: 100% !important; } 
@page { margin: 0.5cm; } 
p, h2, h3 { orphans: 3; widows: 3; } 
h2, h3 { page-break-after: avoid; } 
} 
#startTimer{ 
position:inherit 
width:75px; 
height:20px; 
top:35px; 
left:25px; 
cursor:pointer 
} 
#stopTimer{ 
position:inherit; 
width:75px; 
height:20px; 
top:10px; 
left:25px; 
cursor:pointer 
} 
#countdownCanvas{ 
border-radius:25px; 
box-shadow:10px 10px 5px #888888; 
}

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