I have updated the script to prevent multiple submissions by disabling all form fields upon a successful submission. I have also provided a demo in a zip file.
There are a ton of options and a ton of configurations for creating a contact form for your website. Some of them good, some of them great. Keep in mind, this is just an example, and should be treated as such. Better spam protection is a good idea, but for now we will stick with a simple to implement option.
Before we begin, you will need a few things already implemented on your site. Provided is their name and link to the CDN file. Place these in the footer of your page above the closing