How to get the date for the last Monday from today?

General
1

Hey guys,

I'm looking for an automated way to get the date for the previous Monday from 'today'

So for example if I check now it would return 27-12-2021 and if I run it in 7 days time it would be 03-12-2021 etc etc

Is anyone able to suggest any nodes that may be able to do this that they're aware off or maybe a JS script way to do this?

2

Using the change node and $moment() in a JSONata expression

[{"id":"21e5e450.ab0664","type":"change","z":"c791cbc0.84f648","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"$moment().isoWeekday(-6)","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":430,"y":440,"wires":[["95b09e83.cfbe38"]]},{"id":"4dd7f307.2c34ec","type":"inject","z":"c791cbc0.84f648","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":220,"y":440,"wires":[["21e5e450.ab0664"]]},{"id":"95b09e83.cfbe38","type":"debug","z":"c791cbc0.84f648","name":"b","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":670,"y":340,"wires":[]}]

expression

$moment().isoWeekday(-6)

[edit] sorry that gets you previous to get the last of the month try

$moment().endOf('month').startOf('isoweek')
3

I'm sure there may be easier ways using libraries like moment, but in vanilla JavaScript, you can do:

let today = new Date();
let previousMonday = new Date(today.getTime() - (((today.getDay()+6)%7) * 1000*60*60*24))

Let's break that down.

  1. First we get a Date object for today.
  2. today.getDay() gives us the day of week, with 0=Sunday, 1=Monday etc
  3. We can use that value to know how many days to go back to get to the previous Monday. Given its 0 indexed from Sunday, we need to subtract 1 from the value so that 0 is Monday... whilst ensuring that Sunday becomes a 6. That's what this bit of modulo maths does: (today.getDay()+6)%7)
  4. Now we know how many days to go back, we get the current time in milliseconds (today.getTime()), then subtract the right number of days worth of milliseconds (1000*60*60*24)
  5. Finally we create a new Date object from that time.
5 Likes
4

In the end I used this instead.

$moment().isoWeekday("Monday")

What that be an issue for any reason?

1 Like
5

Use whichever option you wish.

It's sometimes easier to use a library such as moment, but be aware that 'moment' is being depreciated, and possibly succeeded by a different time/date library in the near future.

Also, you are missing out on a great JavaScript learning experience, which may help you in the future...

6

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