javascript calculate time difference between two timestamps code example

Example 1: javascript calculate time

console.time("timer");   //start time with name = timer
console.timeEnd("timer"); //end timer and log time difference

Example 2: javascript time between two times

You can just subtract the hours right away doing it this way

var valuestart = $("select[name='timestart']").val();
var valuestop = $("select[name='timestop']").val();

//create date format          
var timeStart = new Date("01/01/2007 " + valuestart).getHours();
var timeEnd = new Date("01/01/2007 " + valuestop).getHours();

var hourDiff = timeEnd - timeStart;             
Here's the working fiddle http://jsfiddle.net/VnwF7/4/

UPDATE - to calculate if we are including the next day. Just add the following if block

 if (hourDiff < 0) {
    hourDiff = 24 + hourDiff;
 }
http://jsfiddle.net/gfvhqat9/

Example 3: javascript difference between two dates in days

const diffDays = (date, otherDate) => Math.ceil(Math.abs(date - otherDate) / (1000 * 60 * 60 * 24));

// Example
diffDays(new Date('2014-12-19'), new Date('2020-01-01'));   // 1839