JavaScript 判断是否微信内置浏览器

wechat-browser-detect.js

var isWeixin = false;

if (typeof WeixinJSBridge == "object" && typeof WeixinJSBridge.invoke == "function") {
    isWeixin = true;
} else {
    if (document.addEventListener) {
        document.addEventListener("WeixinJSBridgeReady", function() { isWeixin = true; }, false);
    } else if (document.attachEvent) {
        document.attachEvent("WeixinJSBridgeReady", function() { isWeixin = true; });
        document.attachEvent("onWeixinJSBridgeReady", function() { isWeixin = true; });
    }
}

The detection need to either run after onload event, or need a setTimout for multiple attempt because this variable is not available until the in-app browser / page is completely rendered.

// This should be the most ideal way to detect WeChat inapp browser:

window.onload = function () {
if (typeof WeixinJSBridge == "undefined"){
if( document.addEventListener ){
document.addEventListener('WeixinJSBridgeReady', jsApiCall, false);
}else if (document.attachEvent){
document.attachEvent('WeixinJSBridgeReady', jsApiCall);
document.attachEvent('onWeixinJSBridgeReady', jsApiCall);
}
}else{
jsApiCall();
}
}

function jsApiCall() {
document.getElementById('wxmsg').innerHTML = 'WeixinJSBridge ready';
}

@gordonchanhkk
window.onload是在页面所有资源加载完才执行，往往需要一定的时间t1。
WeixinJSBridge并不是WebView一打开就有了，客户端需要初始化这个对象，同样需要时间t2。
当t1>t2的时候，给WeixinJSBridgeReady添加事件监听是无效的。