Return how long ago an event occurred with respect to current time.

ago.js

const pluralize = function (value){
    return Math.floor(value) > 1 ? 's' : '';
}

function ago(date){
    const now = Math.floor(Date.now()/1000)
    const time = new Date(date)
    if(isNaN(time.getTime())){
        throw new Error(`Passed in date ${date} is not a valid date`)
    }
    const parsed_time = Math.floor(time.getTime()/1000)
    
    const ranges = {
        second: 60, // max of 60 seconds before we get to minute
        minute: 3600, // max of 3600 seconds (60 mins) before we get to hour
        hour: 86400, // max of 86400 seconds (24 hours) before we get to a day
        day: 2592000, // max of 2592000 seconds (30 days) before we get to a day
        month: 31536000, // max of 31536000 seconds (12 months) before we get to a day
    }
    
    const difference = now - parsed_time

    if(difference < 0){
        throw new Error(`Passed in date ${date} is in the future`)
    }

    if (difference < 60){
        return `${difference} second${pluralize(difference)} ago`;
    } else if (difference < 3600){
        return `${Math.floor(difference/ranges.second)} minute${pluralize(difference/ranges.second)} ago`;
    } else if(difference < ranges.hour){
        return `${Math.floor(difference/ranges.minute)} hour${pluralize(difference/ranges.minute)} ago`;
    } else if(difference < ranges.day){
        return `${Math.floor(difference/ranges.hour)} day${pluralize(difference/ranges.hour)} ago`;
    } else if(difference < ranges.month){
        return `${Math.floor(difference/ranges.day)} month${pluralize(difference/ranges.day)} ago`;
    } else{
        return `${Math.floor(difference/ranges.month)} year${pluralize(difference/ranges.month)} ago`;
    }
}

module.exports = ago