Code gives out "strange output" - google-apps-script

Question

I am haveing some trubble witht this code. My output will look somthing like this. "29 days, 29 days, 0 hours, 29 minutes". The only variable outside of the code is toon.lastModified. it can be somthing like 1431769709000 . The task for the code is to tell how mutch time that have passed from now, untill there was a change in the JSON. I got the feeling that the problem is that + is used to add numbers and to set strings into each other.
var nowTime = new Date()
var timeStamp = nowTime.getTime()
var lastModTS = ((timeStamp-toon.lastModified)/1000).toFixed(0)
var lastModS = (lastModTS%60)
var lastModMin = (((lastModTS-lastModS)/60)%60)
var lastModH = (((lastModTS-(lastModS+lastModMin*60))/60)%24)
var lastModDay = (Math.floor((lastModTS-(lastModS+lastModMin*60+lastModH*60^2))/(24*60^2)))
var sinceLastMod=""
if (lastModDay==1){
sinceLastMod=lastModDay+" day, "
} else if (lastModDay>1){
sinceLastMod=lastModDay+" days, "
} if (lastModH==1){
sinceLastMod=sinceLastMod+lastModH+" hour, "
} else if (lastModH==0&&lastModDay==0){
sinceLastMod=""
} else {
sinceLastMod=sinceLastMod+sinceLastMod+lastModH+" hours, "
} if (lastModMin==1){
sinceLastMod=lastModDay+" minute, "
} else if (lastModMin==0&&lastModH==0&&lastModDay==0){
sinceLastMod=">1 minute"
} else if (lastModMin>1){
sinceLastMod=sinceLastMod+lastModMin+" minutes"
}
return sinceLastMod //it does not look like this in the code, as it is retuned in an array
EDIT
found another thing
at the end of lastModDay, Google would not do the expotensial, i had to wright it to 60*60 for it to get it.

Answer 1

This line:
sinceLastMod=sinceLastMod+sinceLastMod+lastModH+" hours, "
Should be:
sinceLastMod=sinceLastMod+lastModH+" hours, "
Remove one of the sinceLastMod variables. You've got it in there twice.