Shorten Time Return Function

Question

I have this function which returns the time that a Tweet was created based on the created_at value that comes when a timeline is pulled. I also check whether or not the tweet was created more than 2 hours ago, and if it was, have an action execute. I was wondering, is there a way that this code could be shortened down because it currently feels very long. I thought about using a switch statement instead of all the ifs, but it didn't really shorten the function down at all.

function timeAgo(dateString) {
   var rightNow = new Date();
   var then = new Date(dateString);
   if ($.browser.msie) {
      then = Date.parse(dateString.replace(/( \+)/, ' UTC$1'));
   }
   var diff = rightNow - then;
   var second = 1000;
   var minute = second * 60;
   var hour = minute * 60;
   var day = hour * 24;
   var week = day * 7;
   if (isNaN(diff) || diff < 0) {
      return "";
   }
   if (diff < second * 2) {
      return {tAgo: "right now", timeCheck: false};
   }
   if (diff < minute) {
      return {tAgo: Math.floor(diff / second) + " seconds ago", timeCheck: false};
   }
   if (diff < minute * 2) {
      return {tAgo: "about 1 minute ago", timeCheck: false};
   }
   if (diff < hour) {
      return {tAgo: Math.floor(diff / minute) + " minutes ago", timeCheck: false};
   }
   if (diff < hour * 2) {
      return {tAgo: "about 1 hour ago", timeCheck: false};
   }
   if (diff < day) {
      return {tAgo: Math.floor(diff / hour) + " hours ago", timeCheck: true};
   }
   if (diff > day && diff < day * 2) {
      return {tAgo: "yesterday", timeCheck: true};
   }
   if (diff < day * 365) {
      return {tAgo: Math.floor(diff / day) + " days ago", timeCheck: true};
   }
   else {
      return {tAgo: "over a year ago", timeCheck: true};
   }
}

Answer 1

Here is how i'd approach it

// Make all those units constants
var SECOND = 1000;
var MINUTE = SECOND * 60;
var HOUR = MINUTE * 60;
var DAY = HOUR * 24;
var YEAR = DAY * 365;

// store the string variations in a table, seperate from the code
TIMES = [
    {min: 0, text: "right now", unit: SECOND},
    {min: 2 * SECOND, text: "@ seconds ago", unit: SECOND},
    {min: MINUTE, text: "about 1 minute ago", unit: MINUTE},
    {min: 2 * MINUTE, text: "@ minutes ago", unit: MINUTE},
    {min: HOUR, text: "about 1 hour ago", unit: HOUR},
    {min: 2 * HOUR, text: "@ hours ago", unit: HOUR},
    {min: DAY, text: "yesterday", unit: DAY},
    {min: 2 * DAY, text: "@ days ago", unit: DAY},
    {min: YEAR, text: "over a year ago", unit: YEAR}
];

// use the table to generate the date
function timeAgoText(diff) {
    var use;
    for(var index = 0, length = TIMES.length; index < length; index++)
    {
        if( TIMES[index].min < diff )
        {
            use = TIMES[index];
        }
    }
    units = Math.floor(diff / use.unit)
    return use.text.replace("@", units)
}

function timeAgo(dateText)
{
   var then = new Date(dateString);
   if ($.browser.msie) {
      then = Date.parse(dateString.replace(/( \+)/, ' UTC$1'));
   }
   var diff = new Date() - then;
   if( isNaN(diff) || diff < 0 )
   {
       return ""
   }
   else
   {
       // seperate the time check and the text generation
       return {
           tAgo: timeAgoText(diff),
           timeCheck: diff > HOUR * 2 
       }
   }
}

Answer 2

This doesn't really shorten it, but I think it reads better if you get rid of the diff variable and instead calculate the diff in terms of seconds, minutes, hours and days:

function timeAgo(dateString) {
    var rightNow = new Date(), then = new Date(dateString), seconds, minutes, hours, days;
    if ($.browser.msie) {
        then = Date.parse(dateString.replace(/( \+)/, ' UTC$1'));
    }
    seconds = (rightNow - then) / 1000;
    if (isNaN(seconds) || seconds < 0) {
        return "";
    }
    if (seconds < 2) {
        return {tAgo: "right now", timeCheck: false};
    }
    if (seconds < 60) {
        return {tAgo: Math.floor(seconds) + " seconds ago", timeCheck: false};
    }

    minutes = seconds / 60;
    if (minutes < 2) {
        return {tAgo: "about 1 minute ago", timeCheck: false};
    }
    if (minutes < 60) {
        return {tAgo: Math.floor(minutes) + " minutes ago", timeCheck: false};
    }

    hours = minutes / 60;
    if (hours < 2) {
        return {tAgo: "about 1 hour ago", timeCheck: false};
    }
    if (hours < 24) {
        return {tAgo: Math.floor(hours) + " hours ago", timeCheck: true};
    }

    days = hours * 24;
    if (days < 2) {
        return {tAgo: "yesterday", timeCheck: true};
    }
    if (days < 365) {
        return {tAgo: Math.floor(days) + " days ago", timeCheck: true};
    }

    return {tAgo: "over a year ago", timeCheck: true};
}

Answer 3

Taking what Bill Barry wrote - I then cleaned up the function a bit, got rid of a few declarations and returns, added error checking for future dates and a couple of test cases. Hope this is something along the lines of what you were looking for.

function timeAgo(dateString) {
    /* removed rightNow, replaced with function call in seconds declaration */
    /* removed seconds, minutes, hours, days declarations, declared below on set */
    /* added new returnVal variable to remove all returns below with 1 return */
    var returnVal, then = new Date(dateString);

    /* left alone */
    if($.browser.msie) then = Date.parse(dateString.replace(/( \+)/, ' UTC$1'));

    /* replaced rightNow in seconds declare with new Date() */
    /* declared variables in place instead of above */
    var seconds = (new Date() - then) / 1000;
    var minutes = seconds / 60;
    var hours = minutes / 60;
    var days = hours * 24;

    /* Check for negative value of seconds (negative indicates a future date) */
    if(seconds < 0) return "";

    /* replaced if statements with ternary operations - might not save much performance wise, but looks cleaner */
    seconds < 2 ? returnVal = {tAgo: "right now", timeCheck: false} :
        seconds < 60 ? returnVal =  {tAgo: Math.floor(seconds) + " seconds ago", timeCheck: false} :
            returnVal =  "";

    minutes < 2 ? returnVal =  {tAgo: "about 1 minute ago", timeCheck: false} : 
        minutes < 60 ? returnVal =  {tAgo: Math.floor(minutes) + " minutes ago", timeCheck: false} : 
            returnVal =  {tAgo: "over a year ago", timeCheck: true};

    hours < 2 ? returnVal =  {tAgo: "about 1 hour ago", timeCheck: false} :
        hours < 24 ? returnVal =  {tAgo: Math.floor(hours) + " hours ago", timeCheck: true} :
            returnVal =  {tAgo: "over a year ago", timeCheck: true};

    days < 2 ? returnVal =  {tAgo: "yesterday", timeCheck: true} :
        days < 365 ? returnVal =  {tAgo: Math.floor(days) + " days ago", timeCheck: true} :
            returnVal =  {tAgo: "over a year ago", timeCheck: true};

        /* Remove JSON.stringify() if you want to return an object */
    return JSON.stringify(returnVal);
}

function testTimeAgo(){
    document.write("For ~Tue Apr 07 22:52:51 +0000 2009~:: " + timeAgo("Tue Apr 07 22:52:51 +0000 2009") + "<br>");
    document.write("For ~Tue July 16 22:52:51 +0000 2012~:: " + timeAgo("Tue July 16 22:52:51 +0000 2012") + "<br>");
    document.write("For ~Tue Apr 07 22:52:51 +0000 2013~:: " + timeAgo("Tue Apr 07 22:52:51 +0000 2013") + "<br>");
    document.write("For ~Tue June 07 22:52:51 +0000 2012~:: " + timeAgo("Tue June 07 22:52:51 +0000 2012") + "<br>");
}

/* Run a few tests */
testTimeAgo();

Without comments or test case, and a couple more improvements:

function timeAgo(dateString) {
    var returnVal, then;

    $.browser.msie ? then = Date.parse(dateString.replace(/( \+)/, ' UTC$1')) : then = new Date(dateString);

    var seconds = new Date() - then) / 1000;
    var minutes = seconds / 60;
    var hours = minutes / 60;
    var days = hours * 24;

    if(seconds < 0) return "";

    seconds < 2 ? returnVal = {tAgo: "right now", timeCheck: false} :
        seconds < 60 ? returnVal =  {tAgo: Math.floor(seconds) + " seconds ago", timeCheck: false} :
            returnVal =  "";

    minutes < 2 ? returnVal =  {tAgo: "about 1 minute ago", timeCheck: false} : 
        minutes < 60 ? returnVal =  {tAgo: Math.floor(minutes) + " minutes ago", timeCheck: false} : 
            returnVal =  {tAgo: "over a year ago", timeCheck: true};

    hours < 2 ? returnVal =  {tAgo: "about 1 hour ago", timeCheck: false} :
        hours < 24 ? returnVal =  {tAgo: Math.floor(hours) + " hours ago", timeCheck: true} :
            returnVal =  {tAgo: "over a year ago", timeCheck: true};

    days < 2 ? returnVal =  {tAgo: "yesterday", timeCheck: true} :
        days < 365 ? returnVal =  {tAgo: Math.floor(days) + " days ago", timeCheck: true} :
            returnVal =  {tAgo: "over a year ago", timeCheck: true};

    return returnVal;
}

Answer 4

Two words: Use functions.

/** @const */
var ONE_SECOND = 1000;
/** @const */
var ONE_MINUTE = ONE_SECOND * 60;
/** @const */
var ONE_HOUR = ONE_MINUTE * 60;
/** @const */
var ONE_DAY = ONE_HOUR * 24;
/** @const */
var ONE_WEEK = ONE_DAY * 7;
/** @const */
var ONE_YEAR = ONE_DAY * 365;

function createSingularOrPlural(singular, plural, value, divisor) {
    value = Math.floor(value / divisor);

    return value < 2 ? singular : plural.replace('?', value);
}

function getPrettyTimeAgo(timeAgo) {

    if (timeAgo >= ONE_YEAR) {
        return "over a year ago";
    }

    if (timeAgo >= ONE_DAY) {
        return createSingularOrPlural("yesterday", "? days ago", timeAgo, ONE_DAY);
    }

    if (timeAgo >= ONE_HOUR) {
        return createSingularOrPlural("about 1 hour ago", "? hours ago", timeAgo, ONE_HOUR);
    }

    if (timeAgo >= ONE_MINUTE) {
        return createSingularOrPlural("about 1 minute ago", "? minutes ago", timeAgo, ONE_MINUTE);
    }

    return createSingularOrPlural("right now", "? seconds ago", timeAgo, ONE_SECOND);
}

function getMillisecondsSinceDate(dateString) {
    var rightNow = new Date();
    var then = new Date(dateString);

    // If we're using jQuery, check if we're using IE to perform a defect fix. 
    if (window.$ && window.$.browser && window.$.browser.msie) {
        then = Date.parse(dateString.replace(/( \+)/, ' UTC$1'));
    }

    return rightNow - then;
}

function timeAgo(dateString) {

    var timeDifference = getMillisecondsSinceDate(dateString);

    if (isNaN(timeDifference) || timeDifference < 0) {
        return "";
    }

    return {
        tAgo: getPrettyTimeAgo(timeDifference),
        timeCheck: timeDifference >= 2 * ONE_HOUR
    };
}