If your dateString is RFC282 and ISO8601 compliant:
pass your string into the Date Constructor:
const dateString = "2020-10-30T12:52:27+05:30"; // ISO8601 compliant dateString
const D = new Date(dateString); // {object Date}
from here you can extract the desired values by using Date Getters:
D.getMonth() + 1 // 10 (PS: +1 since Month is 0-based)
D.getDate() // 30
D.getFullYear() // 2020
If you use a non standard date string:
destructure the string into known parts, and than pass the variables to the Date Constructor:
new Date(year, monthIndex [, day [, hours [, minutes [, seconds [, milliseconds]]]]])
const dateString = "30/10/2020 12:52:27";
const [d, M, y, h, m, s] = dateString.match(/\d+/g);
// PS: M-1 since Month is 0-based
const D = new Date(y, M-1, d, h, m, s); // {object Date}
D.getMonth() + 1 // 10 (PS: +1 since Month is 0-based)
D.getDate() // 30
D.getFullYear() // 2020