js判断是否是微信内置浏览器

//判断是否微信登陆
    function isWeiXin() {
        var ua = window.navigator.userAgent.toLowerCase();
        console.log(ua);//mozilla/5.0 (iphone; cpu iphone os 9_1 like mac os x) applewebkit/601.1.46 (khtml, like gecko)version/9.0 mobile/13b143 safari/601.1
        if (ua.match(/MicroMessenger/i) == 'micromessenger') {
            return true;
        } else {
            return false;
        }
    }
    if (isWeiXin()) {
        alert(" 是来自微信内置浏览器")
    } else {
        alert("不是来自微信内置浏览器")
    }