javascript convert dates format

Question

I am facing an issue in javascript dates. I want to display previous and after 30min

How should I added previous or after 30min in current dates.

this.setState({
    current: new Date().toLocaleTimeString(), //10:30:02 PM
    slotTime: new Date().toLocaleTimeString([], {
        hour: '2-digit',
        minute: '2-digit'
    }), //10:30 AM

Output:

10:30 AM  //current date

expected:

10:00 AM   //previous
10:30 AM   //current
11:00 AM   //after 30min

anyone help me?

banguncool · Answer 1 · 2020-05-14T09:48:21.847

Hope this help

/* required:
  * - timestamp => number of timestamp format
  * - format => return format, ex. format 1 (23:59:59), format 2 (23:59)
  * return: time with string
  */
  function timestampToTime(timestamp, format = 1) {
    if (!isNaN(timestamp) || timestamp != undefined) {
      let dd = new Date(timestamp)

      if (format == 1) {
        return ('00' + dd.getHours()).slice(-2) + ':' + ('00' + dd.getMinutes()).slice(-2) + ':' + ('00' + dd.getSeconds()).slice(-2)
      } else if (format == 2) {
        return ('00' + dd.getHours()).slice(-2) + ':' + ('00' + dd.getMinutes()).slice(-2)
      }
    } else {
      return null
    }
  }

  let dd = + new Date()

  let previous = timestampToTime(dd - (1.8e+6))  // 1.8e+6 = 30 min
  let current = timestampToTime(dd)
  let after = timestampToTime(dd + (1.8e+6))  // 1.8e+6 = 30 min

  console.log(previous)
  console.log(current)
  console.log(after)

it is too long can you make the logic short [@](https://stackoverflow.com/users/5515210/banguncool) — MHasan, May 14 '20 at 07:14
There are a great many timestamp formats for which `isNaN(timestamp)` will return true. The OP is using Date objects so would probably prefer to keep working with Date objects. — RobG, May 14 '20 at 07:23

GoranLegenda · Answer 2 · 2020-05-14T07:23:48.090

You can simply do it like this:

var currDate = new Date();
var dd = new Date().setMinutes(currDate.getMinutes() - 30); //reduce 30 minutes
var ddPLus = new Date().setMinutes(currDate.getMinutes() + 30); //add 30 minutes

var reductedTime = new Date(dd);
var addedTime = new Date(ddPLus);

console.log("Current time: ", new Date().toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' })) //current time
console.log("Reduced time: ", reductedTime.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' })) // reduced time by 30mins
console.log("Added time: ", addedTime.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' })) // added time by 30mins

You might consider using one Date object, then grabbing the "now" timestamp, subtract 30 minutes and get the earlier timestamp, then add an hour to get the later timestamp. :-) — RobG, May 14 '20 at 07:26

javascript convert dates format

2 Answers2