Google Calendar API: get list of free slots on specified day

Question

I need to get list of free slots in my google calendar. Now I am just getting list of events. I am using google calendar npm.

google_calendar.events.list(calObj.         


        

Answer 1

You can get free slots from google calendar in two steps. Using npm google-calendar

1st you have to get all free/busy times in your calendar

var startDate = new Date(),
    endDate = new Date();

var rootStart = startDate,
    rootEnd = endDate;

gcal(<accessToken>).freebusy.query({
    "items":[{
        "id": calObj.name
    }],
    "timeMin": startDate.toISOString(),
    "timeMax": endDate.toISOString(),
    "timeZone": "GMT+0100"
},{
    fields: "calendars,groups,kind,timeMax,timeMin", 
    alt:"json"
}, function(err, data) {
    if(err) return console.log(err)

    // then calculate free slots
    return slotsFromEvents(startDate, data.calendars[<calName>].busy)
})

var interval = 2, // how big single slot should be (in this case 2 hrs) 
freeSlots = []; 

function slotsFromEvents(date,events) {
    events.forEach(function (event, index) { //calculate free from busy times
        if (index == 0 && startDate < event.start) {
            freeSlots.push({startDate: startDate, endDate: event.start});
        }
        else if (index == 0) {
            startDate = event.end;
        }
        else if (events[index - 1].end < event.start) {
            freeSlots.push({startDate: events[index - 1].end, endDate: event.start});
        }

        if (events.length == (index + 1) && event.end < endDate) {
            freeSlots.push({startDate: event.end, endDate: endDate});
        }
    });


    if (events.length == 0) {
        freeSlots.push({startDate: startDate, endDate: endDate});
    }

    var temp = {}, hourSlots = [];
    freeSlots.forEach(function(free, index) {
        var freeHours = new Date(free.endDate).getHours() - new Date(free.startDate).getHours(), freeStart = new Date(free.startDate), freeEnd = new Date(free.endDate);
        while(freeStart.getHours()+freeHours+interval>=0) { // 11 + 4 + 2 >= 0
            if(freeHours>=interval) {
                temp.e = new Date(free.startDate);
                temp.e.setHours(temp.e.getHours()+freeHours);
                temp.s = new Date(free.startDate);
                temp.s.setHours(temp.s.getHours()+freeHours-interval);
                if(temp.s.getHours() >= rootStart.getHours() && temp.e.getHours() <= rootEnd.getHours()) {
                    hourSlots.push({calName: calObj.name, startDate:temp.s, endDate:temp.e});
                    temp = {};
                }
            }
            freeHours--;
        }
    })

    // callBack(freeSlots, hourSlots);
}