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>
© 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: 'courier new', 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 'label' 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 'table' 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 ('mobile first') 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'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;
}
以上就是html5计时器实现方法的详细内容。