feat: add @vant/lazyload pacakge

packages/vant-lazyload/src/index.js

@@ -0,0 +1,40 @@
+import Lazy from './lazy';
+import LazyComponent from './lazy-component';
+import LazyContainer from './lazy-container';
+import LazyImage from './lazy-image';
+
+export const Lazyload = {
+  /*
+   * install function
+   * @param  {App} app
+   * @param  {object} options lazyload options
+   */
+  install(app, options = {}) {
+    const LazyClass = Lazy();
+    const lazy = new LazyClass(options);
+    const lazyContainer = new LazyContainer({ lazy });
+
+    app.config.globalProperties.$Lazyload = lazy;
+
+    if (options.lazyComponent) {
+      app.component('LazyComponent', LazyComponent(lazy));
+    }
+
+    if (options.lazyImage) {
+      app.component('LazyImage', LazyImage(lazy));
+    }
+
+    app.directive('lazy', {
+      beforeMount: lazy.add.bind(lazy),
+      update: lazy.update.bind(lazy),
+      updated: lazy.lazyLoadHandler.bind(lazy),
+      unmounted: lazy.remove.bind(lazy),
+    });
+
+    app.directive('lazy-container', {
+      beforeMount: lazyContainer.bind.bind(lazyContainer),
+      updated: lazyContainer.update.bind(lazyContainer),
+      unmounted: lazyContainer.unbind.bind(lazyContainer),
+    });
+  },
+};