feat: add open & close events (#1101)

docs/.vuepress/components/InfiniteScroll.vue

@@ -0,0 +1,72 @@
+<template>
+  <v-select
+    :options="paginated"
+    :filterable="false"
+    @open="onOpen"
+    @close="onClose"
+    @search="query => search = query"
+    ref="select"
+  >
+    <template #list-footer v-if="hasNextPage">
+      <li ref="load" class="loader">
+        Loading more options...
+      </li>
+    </template>
+  </v-select>
+</template>
+
+<script>
+import countries from '../data/countries';
+import vSelect from '../../../src/components/Select'
+
+export default {
+  name: "InfiniteScroll",
+  components: {vSelect},
+  data: () => ({
+    observer: null,
+    limit: 10,
+    search: ''
+  }),
+  computed: {
+    filtered () {
+      return countries.filter(country => country.includes(this.search));
+    },
+    paginated () {
+      return this.filtered.slice(0, this.limit);
+    },
+    hasNextPage () {
+      return this.paginated.length + 10 < this.filtered.length;
+    },
+  },
+  mounted () {
+    this.observer = new IntersectionObserver(this.infiniteScroll);
+  },
+  methods: {
+    async onOpen () {
+      if (this.hasNextPage) {
+        await this.$nextTick();
+        this.observer.observe(this.$refs.load)
+      }
+    },
+    onClose () {
+      this.observer.disconnect();
+    },
+    async infiniteScroll ([{isIntersecting, target}]) {
+      if (isIntersecting) {
+        const ul = target.offsetParent;
+        const scrollTop = target.offsetParent.scrollTop;
+        this.limit += 10;
+        await this.$nextTick();
+        ul.scrollTop = scrollTop;
+      }
+    }
+  }
+}
+</script>
+
+<style scoped>
+  .loader {
+    text-align: center;
+    color: #bbbbbb;
+  }
+</style>

docs/.vuepress/config.js

@@ -120,6 +120,7 @@ module.exports = {
             ['guide/validation', 'Validation'],
             ['guide/selectable', 'Limiting Selections'],
             ['guide/pagination', 'Pagination'],
+            ['guide/infinite-scroll', 'Infinite Scroll'],
             ['guide/vuex', 'Vuex'],
             ['guide/ajax', 'AJAX'],
             ['guide/loops', 'Using in Loops'],

docs/guide/infinite-scroll.md

@@ -0,0 +1,23 @@
+Vue Select doesn't ship with first party support for infinite scroll, but it's possible to implement
+by hooking into the `open`, `close`, and `search` events, along with the `filterable` prop, and the
+`list-footer` slot.
+
+Let's break down the example below, starting with the `data`.
+
+- `observer` - when the component is mounted, a new `IntersectionObserver` will be set here
+- `limit` - the number of options to display 'per page'
+- `search` - since we've disabled Vue Selects filtering, we'll need to filter options ourselves
+
+When Vue Select opens, the `open` event is emitted and `onOpen` will be called. We wait for
+`$nextTick()` so that the `$ref` we need will exist, then begin observing it for intersection.
+
+The observer is set to call `infiniteScroll` when the `<li>` is completely visible within the list.
+Some fancy destructuring is done here to get the first `ObservedEntry`, and specifically the
+`isIntersecting` & `target` properties. If the `<li>` is intersecting, we increase the `limit`, and
+ensure that the scroll position remains where it was before the list size changed. Again, it's
+important to wait for `$nextTick` here so that the DOM elements have been inserted before setting
+the scroll position.
+
+<InfiniteScroll />
+
+<<< @/.vuepress/components/InfiniteScroll.vue

src/components/Select.vue

@@ -619,6 +619,10 @@
        */
       multiple() {
         this.clearSelection()
+      },
+
+      open(isOpen) {
+        this.$emit(isOpen ? 'open' : 'close');
       }
     },