Is it possible to know how long a user has spent on a page?

Question

Say I've a browser extension which runs JS pages the user visits.

Is there an "outLoad" event or something of the like to start counting and see how long the user has spent on a page?

Answer 1

I am assuming that your user opens a tab, browses some webpage, then goes to another webpage, comes back to the first tab etc. You want to calculate exact time spent by the user. Also note that a user might open a webpage and keep it running but just go away. Come back an hour later and then once again access the page. You would not want to count the time that he is away from computer as time spent on the webpage. For this, following code does a docus check every 5 minutes. Thus, your actual time might be off by 5 minutes granularity but you can adjust the interval to check focus as per your needs. Also note that a user might just stare at a video for more than 5 minutes in which case the following code will not count that. You would have to run intelligent code that checks if there is a flash running or something.

Here is what I do in the content script (using 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);
    }
}