🎄How to add interactions to SVG🌟

Dec 15 2023

Back to 2023 Advent Calendar

If you are using mermaidJS or graphviz to generate SVG diagrams, you might want to customize them or add interactions to them.

What you might want to do:

  1. Add a tooltip to a node
  2. Add a link to a node
  3. Highlight on selection or hover
  4. Animate a node on selection
  5. updating styles like colors

How to customize SVG?

Let's start with Basics. SVG is just a markup language like HTML.

  • So you can use CSS to style it.
  • You can also use JavaScript to add interactions to it.
  • Or you just edit it directly.

Given that browser just renders it, it will immediately be reflected in UI.

Let's start with some examples:

Generating simplest SVG

Let's start with generating a simple SVG using mermaidJS.

graph TD;

which looks like this:

diagram pic

Changing color on hover (move mouse over)

Given that SVG is just a markup language, you can standard JS document.querySelector* method to select nodes.

in case of mermaidJs, it generates a SVG with g.node elements for each node, and then internal shape for actual node (e.g rect).

So you can select them and add a mouseover event listener to them.

const nodes = document.querySelectorAll('g.node');
nodes.forEach(node => {
    node.addEventListener('mouseover', () => {
        node.childNodes[0].style.fill = 'red';
    node.addEventListener('mouseout', () => {
        node.childNodes[0].style.fill = '#ECECFF';

Better solution would be to just customize that using CSS

g.node:hover rect {
    fill: red;

diagram pic

but we wanted to demonstrate that SVG is just like HTML, easy to modify on the fly.

We'll publish soon a full length post about interactivity on SVG generated by graphviz or mermaidjs.

but that's it for Advent.