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JavaScript JavaScript Basics (Retired) Working With Numbers Numbers and Strings

Stefan Cutajar
Stefan Cutajar
7,747 Points
Posted by Stefan Cutajar
Stefan Cutajar
7,747 Points

converting to hours

Hi , I know this maybe out of subject but was wondering if you want to add time together like 2.25hrs + 8.40hrs that will add up to 10.65. Is it possible to make the decimal start another number after .60? Thanks

2 Answers

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

Floating math doesn't work like that, but you could rescale the fractional part to become actual decimal hours, do the math and then scale it back for display:

var hours = d => Math.trunc(d) + (d - Math.trunc(d)) * 5 / 3;  // convert to decimal hours
var homin = h => Math.trunc(h) + (h - Math.trunc(h)) * 3 / 5;  // convert to hours.minutes
console.log(homin(hours(2.25) + hours(8.40)));                 // shows 11.05

Also, JavaScript has a "Date" object that stores and manipulates time and date as a number of milliseconds:

var showTime = t => `${t.getHours()}:${('0' + t.getMinutes()).slice(-2)}`;
var start = new Date();                                         // start with the current date & time
start.setHours(2, 25, 0, 0);                                    // set specific time
console.log(showTime(start));                                   // shows "2:25"
var then = new Date(start.getTime() + ((8 * 60) + 30) * 60000); // add 8 hours and 30 minutes (in ms)
console.log(showTime(then));                                    // shows "10:05"

Here's a short tutorial on date and time.

Stefan Cutajar
Stefan Cutajar
7,747 Points
Stefan Cutajar
Stefan Cutajar
7,747 Points

Thanks for your time. Looks like I need a bit more experience so I can understand this better