我假设您的用户打开一个标签,浏览一些网页,然后转到另一个网页,返回到第一个标签等.您想要计算用户花费的确切时间.另请注意,用户可能会打开网页并保持其正常运行但只是离开.一小时后回来,然后再次访问该页面.您不希望将他离开计算机的时间计算在网页上花费的时间.为此,下面的代码每5分钟进行一次docus检查.因此,您的实际时间可能会偏离5分钟的粒度,但您可以根据需要调整间隔以检查焦点.另请注意,用户可能只是盯着视频超过5分钟,在这种情况下,以下代码将不计算在内.您必须运行智能代码来检查是否有闪存运行或其他东西.

这是我在内容脚本中所做的(使用jQuery)：

$(window).on('unload',window_unfocused);
$(window).on("focus",window_focused);
$(window).on("blur",window_unfocused);
setInterval(focus_check,300 * 1000);

var start_focus_time = undefined;
var last_user_interaction = undefined;

function focus_check() {
    if (start_focus_time != undefined) {
        var curr_time = new Date();
        //Lets just put it for 4.5 minutes                                                                                
    if((curr_time.getTime() - last_user_interaction.getTime()) > (270 * 1000)) {
            //No interaction in this tab for last 5 minutes. Probably idle.                                               
            window_unfocused();
        }
    }
}

function window_focused(eo) {
    last_user_interaction = new Date();
    if (start_focus_time == undefined) {
    start_focus_time = new Date();                                                               
    }
}

function window_unfocused(eo) {
    if (start_focus_time != undefined) {
    var stop_focus_time = new Date();
    var total_focus_time = stop_focus_time.getTime() - start_focus_time.getTime();
    start_focus_time = undefined;
    var message = {};
        message.type = "time_spent";
        message.domain = document.domain;
        message.time_spent = total_focus_time;
        chrome.extension.sendMessage("",message);
    }
}