Clone moment js object

Question

I have momentjs object in state

  state = {
     startDate: getNow() //this funtion return a momemtJS object
    }

in one function, I need to get the date one year before startDate

const dateBeforeOneYear = this.state.startDate.subtract(1, 'years');

But if I do like this, I modify the state by mistake

So I try to copy the state

const copyStartDate = {...this.state.startDate}

const copyStartDate = this.state.startDate.subtract(1, 'years');

But now I get the error, substract is not a function, I guess because copyStartDate is no more MomemntJs

Answer 1

There's a method to clone a moment object:

const yearBefore = this.state.startDate.clone().subtract(1, 'years');

It would also be a better idea to store a serialisable representation of the date in your component state, such as the result of calling .valueOf() on either a Date or a Moment, either of which returns the number of milliseconds since the UNIX epoch.

Answer 2

moment.js has its own api for cloning moment object.

var copy = momentObj.clone();

And I agree on storing dates serialize representation instead of Object in store.

Answer 3

It's also possible to copy a moment object through it's constructor. Like so

const firstMoment = moment("2020-08-18");
const clone = moment(firstMoment);