**[ This description is mirrored from README.md at [github.com/reach-digital/polymer-matryoshka-loader](https://github.com//reach-digital/polymer-matryoshka-loader/blob/0.8.0/README.md) on 2019-05-22 ]** # Matryoshka Loading Mixin Defines a loading flag for elements that automatically take into account the loading state of its child elements. The element implementing MatryoshkaLoaderMixin gains a few interesting Boolean properties: - `hostLoading` (flag to be set when your element is loading) - `loading` (this.hostLoading || this._areChildrenLoading()) - `loaded` (!loading) ```html 1 1 ``` ## Implementing it your own element ```js class YourCustomElement extends MatryoshkaLoaderMixin(Polymer.Element) { static get is() { return 'your-custom-element' } connectedCallback() { super.connectedCallback(); //Do your expensive operation Polymer.Async.timeOut.run(_ => { //When you're done: this.hostLoading = false; }); } } customElements.define(YourCustomElement.is, YourCustomElement) ```