js--判断当前环境是否为iphonex环境

    /**
     * 判断是否是iphonex
     */
    function getIsIphonex () {
        var u = navigator.userAgent;
        var isIOS = !!u.match(/\(i[^;]+;( U;)? CPU.+Mac OS X/);
        if (isIOS) {
            if (screen.height == 812 && screen.width == 375) {
                return true;
            }
            else {
                return false;
            }
        }
    };