var imgUrl = ‘http://su.bdimg.com/static/superplus/img/logo_white.png‘;//这里是分享的时候的那个图片
var lineLink = ‘http://baidu.com‘;//这个是分享的网址
var descContent = "这个操作的介绍，没发现他有啥用";
var shareTitle = ‘这是题目题目题目‘;
var appid = ‘wxc9937e3a66af6dc8‘;  //这里写开发者接口里的appid
function shareFriend() {
    WeixinJSBridge.invoke(‘sendAppMessage‘,{
                            "appid": appid,
                            "img_url": imgUrl,
                            "img_width": "640",
                            "img_height": "640",
                            "link": lineLink,
                            "desc": descContent,
                            "title": shareTitle
                            }, function(res) {
                            _report(‘send_msg‘, res.err_msg);
                            })
}
function shareTimeline() {
    WeixinJSBridge.invoke(‘shareTimeline‘,{
                            "img_url": imgUrl,
                            "img_width": "640",
                            "img_height": "640",
                            "link": lineLink,
                            "desc": descContent,
                            "title": shareTitle
                            }, function(res) {
                            _report(‘timeline‘, res.err_msg);
                            });
}
function shareWeibo() {
    WeixinJSBridge.invoke(‘shareWeibo‘,{
                            "content": descContent,
                            "url": lineLink,
                            }, function(res) {
                            _report(‘weibo‘, res.err_msg);
                            });
}
// 当微信内置浏览器完成内部初始化后会触发WeixinJSBridgeReady事件。
document.addEventListener(‘WeixinJSBridgeReady‘, function onBridgeReady() {
        // 发送给好友
        WeixinJSBridge.on(‘menu:share:appmessage‘, function(argv){
            shareFriend();
            });
        // 分享到朋友圈
        WeixinJSBridge.on(‘menu:share:timeline‘, function(argv){
            shareTimeline();
            });
        // 分享到微博
        WeixinJSBridge.on(‘menu:share:weibo‘, function(argv){
            shareWeibo();
            });
        }, false);

这堆代码在你在手动触发右上角按钮中的功能时候生效，在于 WeixinJSBridge.on 这个功能上

微信浏览器自带WeixinJSBridge 指定分享内容