I always seem to find myself landing here only to realize that the title and question are not quite aligned.
If you want a moment date from a string:
const myMomentObject = moment(str, 'YYYY-MM-DD')
From moment documentation:
Instead of modifying the native Date.prototype, Moment.js creates a wrapper for the Date object.
If you instead want a javascript Date object from a string:
const myDate = moment(str, 'YYYY-MM-DD').toDate();