feat(component): add side menu component

This component can track position of element within scrollable element.

src/components/SideMenu.vue

@@ -0,0 +1,119 @@
+<script lang="ts" setup>
+import { onUnmounted } from 'vue';
+import { ref } from 'vue';
+import { onMounted } from 'vue';
+
+type Menu = {
+  element?: HTMLElement;
+  anchor: string;
+  name: string;
+};
+
+const props = defineProps<{
+  menu: Menu[];
+
+  scrollElement?: Element | HTMLElement | string;
+
+  foreground?: string;
+  background?: string;
+
+  active?: {
+    foreground?: string;
+    background?: string;
+  };
+}>();
+
+const scrollElement = ref<Element | HTMLElement>();
+
+function handleClick(menu: Menu) {
+  const element = document.getElementById(menu.anchor);
+
+  if (element) {
+    element.scrollIntoView({
+      behavior: 'smooth',
+      block: 'center',
+    });
+  }
+}
+
+const activeMenu = ref(props.menu.at(0)?.anchor || '');
+
+function onScroll() {
+  let current = '';
+
+  if (!scrollElement.value) return;
+
+  const container = scrollElement.value;
+
+  props.menu.forEach((v) => {
+    if (!v.element) v.element = document.getElementById(v.anchor) || undefined;
+    if (!v.element) return;
+
+    if (
+      container.scrollTop + container.clientHeight / 2 >
+      v.element.offsetTop
+    ) {
+      current = v.anchor;
+    }
+  });
+
+  activeMenu.value = current;
+}
+
+onMounted(() => {
+  if (typeof props.scrollElement === 'string' || !props.scrollElement) {
+    const element = document.querySelector(props.scrollElement || 'body');
+    if (element) scrollElement.value = element;
+  } else {
+    scrollElement.value = props.scrollElement;
+  }
+
+  scrollElement.value?.addEventListener('scroll', onScroll);
+});
+onUnmounted(() => {
+  scrollElement.value?.removeEventListener('scroll', onScroll);
+});
+</script>
+
+<template>
+  <div class="side-menu__container">
+    <span
+      :style="{
+        '--side-menu__fg': activeMenu !== v.anchor ? foreground : undefined,
+        '--side-menu__bg': activeMenu !== v.anchor ? background : undefined,
+        '--side-menu__fg-active': active?.foreground,
+        '--side-menu__bg-active': active?.background,
+      }"
+      class="side-menu__item"
+      :class="{ 'side-menu__active': activeMenu === v.anchor }"
+      v-for="v in menu"
+      @click="handleClick(v)"
+    >
+      {{ v.name }}
+    </span>
+  </div>
+</template>
+
+<style scoped>
+.side-menu__container {
+  display: flex;
+  flex-direction: column;
+  gap: var(--size-1);
+  padding: var(--size-2);
+
+  & > .side-menu__item {
+    transition: 0.3s background ease-in-out;
+    color: var(--side-menu__fg, inherit);
+    background: var(--side-menu__bg, inherit);
+    padding: var(--size-2) var(--size-4);
+    border-radius: var(--radius-2);
+    cursor: pointer;
+
+    &.side-menu__active {
+      --side-menu__fg: var(--side-menu__fg-active, inherit);
+      --side-menu__bg: var(--side-menu__bg-active, inherit);
+      font-weight: 600;
+    }
+  }
+}
+</style>