I know it is a question for JavaScript but "Is there a way I can achieve the same?" motivated me to answer this. You can use Selenium for automated form filling.
Here is a working script to fill the form using selenium in Python. Hope this will help you out.
from selenium import webdriver
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.support.ui import Select
import time
driver = webdriver.Chrome()
driver.get("http://www.rmlau.site/urn_r/Registration.aspx")
# Students information, loading from excel, csv whatsoever
name = "John Doe"
moName = "Jane"
faName = "Doe Doe"
dob = "17071997"
email = "foo@foo.com"
mobileNo = "090078601"
adharNo = "1231"
course = 'B.Sc. Part One'
time.sleep(3)
# Fill Form
driver.find_element_by_id("ctl00_ContentPlaceHolder1_txtName").send_keys(name)
driver.find_element_by_id("ctl00_ContentPlaceHolder1_txtMotherName").send_keys(moName)
driver.find_element_by_id("ctl00_ContentPlaceHolder1_txtFatherName").send_keys(faName)
driver.find_element_by_id("ctl00_ContentPlaceHolder1_txtEmail").send_keys(email)
driver.find_element_by_id("ctl00_ContentPlaceHolder1_txtMobilNo").send_keys(mobileNo)
driver.find_element_by_id("ctl00_ContentPlaceHolder1_txtAdhar").send_keys(adharNo)
select = Select(driver.find_element_by_id('ctl00_ContentPlaceHolder1_ddl_course'))
select.select_by_visible_text(course)
driver.find_element_by_id("ctl00_ContentPlaceHolder1_txtDOB").send_keys(dob)
driver.find_element_by_id("ctl00_ContentPlaceHolder1_txtDOB").clear()
driver.find_element_by_id("ctl00_ContentPlaceHolder1_txtDOB").send_keys(dob)
# Submit
driver.find_element_by_id("ctl00_ContentPlaceHolder1_btnsave").click()