angular-hmr: Hot Module Replacement for Webpack and Angular


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49333Apr 30, 2021Mar 21, 2016Minified + gzip package size for @angularclass/hmr in KB


Angular HMR

Angular Hot Module Replacement

Angular-HMR Hot Module Reloading for Webpack and Angular. All versions of Angular and Webpack will work with this module

npm install @angularclass/hmr



import { removeNgStyles, createNewHosts, bootloader } from '@angularclass/hmr';

  bootstrap: [ App ],
  declarations: [ App ],
  imports: [
    // Angular 2
    RouterModule.forRoot([], {
      useHash: true
    // app
    // vendors
  providers: []
class MainModule {
  constructor(public appRef: ApplicationRef) {}
  hmrOnInit(store) {
    if (!store || !store.state) return;
    console.log('HMR store', store);
    console.log('store.state.data:', store.state.data)
    // inject AppStore here and update it
    // this.AppStore.update(store.state)
    if ('restoreInputValues' in store) {
    // change detection
    delete store.state;
    delete store.restoreInputValues;
  hmrOnDestroy(store) {
    var cmpLocation = this.appRef.components.map(cmp => cmp.location.nativeElement);
    // recreate elements
    store.disposeOldHosts = createNewHosts(cmpLocation)
    // inject your AppStore and grab state then set it on store
    // var appState = this.AppStore.get()
    store.state = {data: 'yolo'};
    // store.state = Object.assign({}, appState)
    // save input values
    store.restoreInputValues  = createInputTransfer();
    // remove styles
  hmrAfterDestroy(store) {
    // display new elements
    delete store.disposeOldHosts;
    // anything you need done the component is removed

export function main() {
  return platformBrowserDynamic().bootstrapModule(MainModule)
    // use `hmrModule` or the "@angularclass/hmr-loader"
    .then((ngModuleRef: any) => {
      // `module` global ref for webpackhmr
      // Don't run this in Prod
      return hmrModule(ngModuleRef, module);

// boot on document ready

bootloader is only needed to detect that the dom is ready before bootstraping otherwise bootstrap. This is needed because that dom is already ready during reloading.

Important Helpers

  • removeNgStyles: remove angular styles
  • createNewHosts and disposeOldHosts: recreate root elements for bootstrapping
  • bootloader: boot on document ready or boot if it's already ready
  • createInputTransfer and restoreInputValues: transfer input DOM state during replacement


In production you only need bootloader which just does this:

export function bootloader(main) {
  if (document.readyState === 'complete') {
  } else {
    document.addEventListener('DOMContentLoaded', main);

You would bootstrap your app the normal way, in production, after dom is ready. Also, in production, you should remove the loader:

@NGRX/platform (NGRX 4.x.x)

To hook into NGRX 4 you simply need to supply a reducer to set the state, and include it in your development metaReducers.

// make sure you export for AoT
export function stateSetter(reducer: ActionReducer<any>): ActionReducer<any> {
  return function(state: any, action: any) {
    if (action.type === 'SET_ROOT_STATE') {
      return action.payload;
    return reducer(state, action);

In your root reducer you can do something like this to include it in your metaReducers. You should access your environment here and only include this in development.

 * By default, @ngrx/store uses combineReducers with the reducer map to compose
 * the root meta-reducer. To add more meta-reducers, provide an array of meta-reducers
 * that will be composed to form the root meta-reducer.
export const metaReducers: ActionReducer<any, any>[] = [stateSetter]

Simply supply the metaReducer to the StoreModule and your hmr is hooked in.

 StoreModule.forRoot(reducers, { metaReducers }),

enjoy — PatrickJS

If you find any bugs or have a feature request, please open an issue on github!

The npm package download data comes from npm's download counts api and package details come from npms.io.