1.用web-worker实现:另起一个线程,将计数工作运行在后台的JavaScript文件,并返回累加后的结果。
该js文件运行于后台,独立于其他脚本,不会影响页面的性能。html页面可以继续做任何事情,而此时web worker在后台运行,互不干扰。
在用chrome调试时候出现错误:
Uncaught SecurityError: Failed to construct ‘Worker‘: Script at ‘file:///Users/***/Desktop/myworker.js‘ cannot be accessed from origin ‘null‘.
原因在于:“Chrome doesn‘t let you load web workers when running scripts from a local file. Note: Firefox won‘t work either. Try Safari. ”;
附上链接:http://stackoverflow.com/questions/21408510/chrome-cant-load-web-worker
2.根据用户输入时间间隔来计数,比如输入1000,则每隔一秒计数一次;
3.test.html用postmessage向myworkers.js传消息,并用onmessage方法收消息;
myworkers.js用postmessage给test.html发消息,但是通过self.addEventListener(‘message‘, function(e){});来捕获message事件,获取test.html发来的消息。通常我们用window.addEventListener(‘message‘,function(e){});来添加消息事件,但是web worker不支持window object(http://stackoverflow.com/questions/11219775/global-variable-in-web-worker),所以只能用self;
test.html页面如下:
<html> <script type="text/javascript"> var myworker; var i = 10; myworker = new Worker("./myworker.js"); myworker.onmessage = function(event){ document.getElementById("result").innerHTML = event.data; } function countStart(){ var value = document.getElementById("textinput").value; myworker.postMessage({"moustevent":1,"textinput":value});//1 start count } function countStop(){ myworker.postMessage({"moustevent":0}); } </script> <style type="text/css"> .countTime{ width:100px; height:100px; background-color:blue; } </style> <body> <p>Count numbers: <output id="result"></output></p> <div class="countTime" id="countTime" onmouseover="countStart()" onmouseout="countStop()"></div> <p>Please Input Interval Time:</p> <input id="textinput" type="number" ></input> </body> </html>
注意:
如果想post多个参数,可以考虑post一个json过去;
myworker.js
var i = 1; var pid = 0; var tmp; function countTime(){ i+=1; postMessage(i); }; //add event listener to handle the different message self.addEventListener(‘message‘, function(e){ //if message == 1 start count tmp = e.data["textinput"]; if(1 == e.data["moustevent"]){ if(tmp <= 0) tmp = 1000; pid = setInterval(countTime, tmp); } //if message == 0 stop count else{ clearInterval(pid); } });
注意:
要clearInterval必须有个id指明注销那个interval,所以定义时pid = setInterval(countTime, tmp);
注销时clearInterval(pid);
如图所示:
1.鼠标放在蓝色框上面开始计时;
2.输入框为600,则每隔600毫秒计数器加一,否则,默认1000毫秒;
3.鼠标移除,停止计数;