问在日期范围内查找可用的天数

EN

// Helper function
function addDays(date, days) {
    return new Date(date.getTime() + days * 24*60*60*1000);
}

// Main function
function gaps(period, events) {
    events = events.slice(0).filter(function (a) {
        // Exclude events which are outside the main period
        return a.to >= period.from && a.from <= period.to;
    }).sort(function (a, b) {
        // Sort events by their starting date
        return a.from - b.from;
    });
    var result = events.reduce(function (result, curr) {
        if (curr.from - result.free > 0) {
            // gap found
            result.gaps.push({
                from: result.free, 
                to:   addDays(curr.from, -1)
            });
        }
        if (curr.to - result.free >= 0) {
            // first free day is after this event
            result.free = addDays(curr.to, 1)
        }
        return result;
    }, { gaps: [], free: period.from } );
    // Potentially add gap between last event end period-end
    if (period.to - result.free >= 0) {
        result.gaps.push({
            from: result.free,
            to:   period.to
        });
    }
    return result.gaps;
}


// Sample data:

var period = {
    from: new Date('2016-01-01'),
    to: new Date('2016-12-31')
};

var events = [
    { from: new Date('2016-02-01'), to: new Date('2016-02-29') },
    { from: new Date('2016-03-01'), to: new Date('2016-03-15') },
    { from: new Date('2016-04-16'), to: new Date('2016-04-30') },
];

// Call to function
var res = gaps(period, events);

// Output in snippet
document.write('<pre>' + JSON.stringify(res, null, 4));

var aprilAvailableDays = [true, true, true, etc...] // a boolean for each day

aprilEvents.forEach(function (event) {
    for (var i = event.startDay; i <= event.endDay; i++) {
        aprilAvailableDays[i] = false;
    }
});