下面是一个案例，有需要的朋友可以拿下来运行参考一下。
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,minimum-scale=1.0,maximum-scale=1.0,user-scalable=no">
<title>判断手机是否安装微信</title>
</head>
<body>
<a href="javascript:testApp('weixin://')" class="dl-btn" id="download">打开微信</a>
<script>
function testApp(url) {
var timeout, t = 1000, hasApp = true;
setTimeout(function () {
if (!hasApp) {
//没有安装微信
var r=confirm("您没有安装微信，请先安装微信!");
if (r==true){
location.href="http://weixin.qq.com/"
}
}else{
//安装微信
}
document.body.removeChild(ifr);
}, 2000)
var t1 = Date.now();
var ifr = document.createElement("iframe");
ifr.setAttribute('src', url);
ifr.setAttribute('style', 'display:none');
document.body.appendChild(ifr);
timeout = setTimeout(function () {
var t2 = Date.now();
if (!t1 || t2 - t1 < t + 100) {
hasApp = false;
}
}, t);
}
</script>
</body>
</html>