houkanshan/test.html

## test.html
<!DOCTYPE HTML>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title></title>
    <script src="./test.js" type="text/javascript"></script>
</head>
<body>
	<span id="test"></span>
</body>
</html>

## test.js
/*
 * http://www.douban.com/people/2790109/status/1004046271/
 * 一个应用多个实例间只允许一个实例运行
 * localStorage.clear()的时候会出问题，没有做恢复~
 * runner其实不需要每次都检查localStorage.runningId
 */
window.onload  = function(){
    // if localStorage.clear(), all will be stoped,
    // create a new page will restart

    testEl = document.getElementById('test');

    var CHECK_TIME = 500;
    var TIMEOUT_TIME = 1000;

    var myId;
    var runningId = parseInt(localStorage.runningId, 10);
    var lastRunnerId = parseInt(localStorage.lastId, 10);

    //id init
    if(runningId && lastRunnerId){
        myId = lastRunnerId + 1;
    }
    else {
        myId = 1;
        localStorage.runningId = myId;
    }
    localStorage.lastId = myId;
    localStorage.timeStamp = localStorage.timeStamp || Date.now();


    setInterval(function(){
        //check id
        var runningId = parseInt(localStorage.runningId, 10);
        if (runningId === myId){
            // i'm running
            localStorage.timeStamp = Date.now();
            run();
        }
        else {
            // i'm waiting
            if(Date.now() - localStorage.timeStamp > TIMEOUT_TIME){
                // check timeout, be the runner
                localStorage.timeStamp = Date.now();
                localStorage.runningId = myId;
            }
            else{
                // still waiting
                wait();
            }
        }
    }, CHECK_TIME);
};


function run(){
    var msg = 'i\'m runnging';
    testEl.innerText = msg;
    console.log(msg);
};
function wait(){
    var msg = localStorage.runningId + ' is running~';
    testEl.innerTest = msg;
    console.log(msg);
};
	<!DOCTYPE HTML>
	<html lang="en">
	<head>
	<meta charset="UTF-8">
	<title></title>
	<script src="./test.js" type="text/javascript"></script>
	</head>
	<body>
	<span id="test"></span>
	</body>
	</html>
	/*
	* http://www.douban.com/people/2790109/status/1004046271/
	* 一个应用多个实例间只允许一个实例运行
	* localStorage.clear()的时候会出问题，没有做恢复~
	* runner其实不需要每次都检查localStorage.runningId
	*/
	window.onload = function(){
	// if localStorage.clear(), all will be stoped,
	// create a new page will restart

	testEl = document.getElementById('test');

	var CHECK_TIME = 500;
	var TIMEOUT_TIME = 1000;

	var myId;
	var runningId = parseInt(localStorage.runningId, 10);
	var lastRunnerId = parseInt(localStorage.lastId, 10);

	//id init
	if(runningId && lastRunnerId){
	myId = lastRunnerId + 1;
	}
	else {
	myId = 1;
	localStorage.runningId = myId;
	}
	localStorage.lastId = myId;
	localStorage.timeStamp = localStorage.timeStamp \|\| Date.now();


	setInterval(function(){
	//check id
	var runningId = parseInt(localStorage.runningId, 10);
	if (runningId === myId){
	// i'm running
	localStorage.timeStamp = Date.now();
	run();
	}
	else {
	// i'm waiting
	if(Date.now() - localStorage.timeStamp > TIMEOUT_TIME){
	// check timeout, be the runner
	localStorage.timeStamp = Date.now();
	localStorage.runningId = myId;
	}
	else{
	// still waiting
	wait();
	}
	}
	}, CHECK_TIME);
	};


	function run(){
	var msg = 'i\'m runnging';
	testEl.innerText = msg;
	console.log(msg);
	};
	function wait(){
	var msg = localStorage.runningId + ' is running~';
	testEl.innerTest = msg;
	console.log(msg);
	};