// Divide the 13-digit timestamp by 1000 and then round to get a 10-digit timestamp number
parseInt(+new Date()/1000);
 
 // Convert the 13-digit timestamp to a string and intercept the first 10 digits to get a 10-digit timestamp string
 (+new Date()).toString().substring(0,10); // intercept the 0-9th digits
 (+new Date()).toString().substr(0,10); // intercept 10 digits from the 0th position