Should a website UI designer know Javascript/JQuery as well as HTML & CSS?

It's all presentation layer code, and all works together, so a UI designer should know how all 3 work together.

1. Do UI designers need to know JavaScript?
2. Do UI designers need to know HTML?
3. Do UX UI designers use JavaScript?
4. Should a UI designer know how do you code?

Do UI designers need to know JavaScript?

Most UX designers don't need to use programming languages, though some UX designers may need to learn JavaScript to prototype. If you do need to learn programming, a foundation in front-end development will give you a significant advantage.

Do UI designers need to know HTML?

What coding languages do UX/UI designers use? The most common markup languages that UX/UI designers should know are HTML & CSS.

Do UX UI designers use JavaScript?

Now that we know the answer to “Does UX require coding?” we can address a variation of that same question: “Do UX designers code?” For many, the answer is “yes.” Most UX designers have at least a little understanding of code, including HTML, CSS, and Javascript. Other languages like Reach and Swift aren't as important.

Should a UI designer know how do you code?

UI Designers do not need to code, but it is extremely beneficial if you have programming skills. Depending on the nature of the product, it's also not unusual for UI/UX design and development to be intertwined into a single process.