As said before, JavaScript is front-end unless one uses a framework, library or a platform which is built on top of JavaScript to make it back-end such as Node.JS and others, but then you're not using JavaScript are you? Take jQuery for an example, it is built on top of JavaScript to make it easier to create dynamic content however people say they're using jQuery not JavaScript the same way people say they're using Node.JS (instead of JavaScript) which in this instance makes JavaScript (from the OP's context) front-end. If the OP had specified Node.JS then I wouldn't have mentioned it, however since he wrote JavaScript, I did. Node.JS and JavaScript are two different languages (although related) they're different.
I know JavaScript is not limited to the web and I never once stated it is. However mentioning that JavaScript can be used outside of the web had no actual place here as the OP is using it on the web.
Another example, Android (the operating system) is Linux under the hood. However people don't say they're using a Linux phone, they say it is an Android phone.
Hopefully that should clear up what I'm trying to point out. Considering this is a site which he'll be using to get clients, I'm simply pointing out that he should make things clear.