**`Polyfills`** in angular are few lines of code which make your application compatible for different browsers. The code we write is mostly in ES6(New Features: Overview and Comparison) and is not compatible with IE or firefox and needs some environment setups before being able to be viewed or used in these browsers. 

**`Polyfills.ts`** was provided by angular to help you do away with need to specifically setup everything. 

From **`Docs`**

&gt; Angular is built on the latest standards of the web platform.
&gt; Targeting such a wide range of browsers is challenging because they do
&gt; not support all features of modern browsers.

Read more **[`here`][1]**


  [1]: https://angular.io/guide/browser-support

Basically **polyfills** compatible for different browsers especially IE old versions **IE8, IE9 and IE10.** Angular has new features which written in **ES6 and typescript**, so polyfills helps to compatible with different browsers. 

Angular is written in  ES6+ language specification. As many of its features are not supported by all the browsers. So by defining them in polyfill it will be compatible in the given browser.

 This file includes polyfills needed by Angular and is loaded before the app.
 You can add your own extra polyfills to this file.
 
 This file is divided into 2 sections:
  1. Browser polyfills. These are applied before loading ZoneJS and are sorted by browsers.
    2. Application imports. Files imported after ZoneJS should be loaded before your main file.

I have some (simplified) code that uses Java Optionals:

    Optional&lt;User&gt; maybeTarget = userRepository.findById(id1);
    Optional&lt;String&gt; maybeSourceName = userRepository.findById(id2).map(User::getName);
    Optional&lt;String&gt; maybeEventName = eventRepository.findById(id3).map(Event::getName);

    maybeTarget.ifPresent(target -&gt; {
        maybeSourceName.ifPresent(sourceName -&gt; {
            maybeEventName.ifPresent(eventName -&gt; {
                sendInvite(target.getEmail(), String.format(&quot;Hi %s, $s has invited you to $s&quot;, target.getName(), sourceName, meetingName));
            }
        }
    }

Needless to say, this looks and feels bad. But I can&#39;t think of another way to do this in a less-nested and more readable way. I considered streaming the 3 Optionals, but discarded the idea as doing a `.filter(Optional::isPresent)` then a `.map(Optional::get)` feels even worse.

So is there a better, more &#39;Java 8&#39; or &#39;Optional-literate&#39; way of dealing with this situation (essentially **multiple Optionals all needed to compute a final operation**)?

How to use Java 8 Optionals, performing an action if all three are present?

The standard way AFAIK to return data in ASP.NET Core Web Api is by using `IActionResult` and providing e.g. an `OkObject` result. This works fine with objects, but what if I have obtained a JSON string somehow, and I just want to return that JSON back to the caller?

e.g. 


    public IActionResult GetSomeJSON()
    {
        return Ok(&quot;{ \&quot;name\&quot;:\&quot;John\&quot;, \&quot;age\&quot;:31, \&quot;city\&quot;:\&quot;New York\&quot; }&quot;);
    }

What ASP.NET Core does here is, it takes the JSON String, and wraps it into JSON again (e.g. it escapes the JSON)

Returning plain text with `[Produces(&quot;text/plain&quot;)]` does work by providing the &quot;RAW&quot; content, but it also sets the content-type of the response to PLAIN instead of JSON. We use `[Produces(&quot;application/json&quot;)]` on our Controllers.

How can I return the JSON that I have as a normal JSON content-type without it being escaped?

*Note: It doesn&#39;t matter how the JSON string was aquired, it could be from a 3rd party service, or there are some special serialization needs so that we want to do custom serialization instead of using the default JSON.NET serializer.*

Return &quot;raw&quot; json in ASP.NET Core 2.0 Web Api

polyfills.ts file is auto generated while creating an Angular application using Angular Cli.
Can anyone explain me what is the use of polyfills.ts file in Angular application.

What is the use of polyfills.ts file in Angular

<p>polyfills.ts file is auto generated while creating an Angular application using Angular Cli.
Can anyone explain me what is the use of polyfills.ts file in Angular application.</p>


I&#39;ve created a form in a dialog using material forms, but I can&#39;t seem to get the inputs to be wider than 180px despite following numerous examples including https://material.angular.io/components/input/example.

I&#39;m sure this is a pretty standard CSS thing, but I don&#39;t have that sort of brain so I cant figure out the problem.  

Does anyone have a serious / non-trivial example that works??

Here&#39;s mine:

    &lt;h1 mat-dialog-title&gt;{{title}}&lt;/h1&gt;
    &lt;mat-dialog-content&gt;
      &lt;form novalidate #f=&quot;ngForm&quot; class=&quot;form-full-width&quot;&gt;
        &lt;mat-form-field class=&quot;input-full-width&quot;&gt;
          &lt;input type=&quot;text&quot; [(ngModel)]=&quot;data.name&quot; name=&quot;name&quot; matInput placeholder=&quot;Name&quot;&gt;
          &lt;mat-hint&gt;Enter a unique name.&lt;/mat-hint&gt;
        &lt;/mat-form-field&gt;
        &lt;mat-form-field class=&quot;input-full-width&quot;&gt;
          &lt;textarea [(ngModel)]=&quot;data.description&quot; name=&quot;description&quot; matInput placeholder=&quot;Description&quot;&gt;&lt;/textarea&gt;
          &lt;mat-hint&gt;You should describe the purpose/use of this thing.&lt;/mat-hint&gt;
        &lt;/mat-form-field&gt;
      &lt;/form&gt;
    &lt;/mat-dialog-content&gt;

CSS :

    .form-full-width {
        min-width: 150px;
        max-width: 500px;
        width:100%;
    }

    .input-full-width {
        width:800px;
    }

    .mat-form-field.mat-form-field {
        width: auto;
    }

Thanks.

angular 5 material - form fields stuck at 180px

I have created a angular project with  Angular CLI: 1.6.3 Node: 9.4.0
OS: linux x64 version. But when want to run my angular app with command ng serve then fetch this error 

&gt; Cannot find module &#39;@angular-devkit/core&#39;.

 


Cannot find module &#39;@angular-devkit/core&#39;

I am trying to build this template:

&lt;!-- language: lang-html --&gt;

    &lt;ul&gt;
        &lt;li *ngFor=&#39;let link of links&#39;&gt;
            &lt;ng-container *ngIf=&quot;link.type == &#39;complex&#39;; then complexLink else simpleLink&quot;&gt;&lt;/ng-container&gt;
        &lt;/li&gt;
    &lt;/ul&gt;
    
    &lt;ng-template #simpleLink&gt;
        ...
        {{ link.some_property }}
    &lt;/ng-template&gt;
    
    &lt;ng-template #complexLink&gt;
        ...
        {{ link.some_property }}
    &lt;/ng-template&gt;

The problem is that the link variable is undefined inside the ng-template so I get an error of accessing &#39;some_property&#39; of undefined.

I am struggeling to understand how I pass the link variable from the ngFor to the ng-template

It would be great to know if there are multiple solutions for this problem.

Angular - ng-template with parameter inside ngIf inside ngFor

How would I remove a query parameter from the URL? For example from `www.expample.com/home?id=123&amp;pos=sd&amp;sd=iii` to `www.expample.com/home?id=123&amp;sd=iii`

EDIT:
This is my version:

    this.activatedRoute.queryParams.subscribe(c =&gt; {
      const params = Object.assign({}, c);
      delete params.dapp;
      this.router.navigate([], { relativeTo: this.activatedRoute, queryParams: params });
    }).unsubscribe();


Angular 5 remove query param

I keep getting the following errors when running unit tests

    Error: StaticInjectorError(DynamicTestModule)[ApiService -&gt; HttpClient]: 
    	  StaticInjectorError(Platform: core)[ApiService -&gt; HttpClient]: 
    	    NullInjectorError: No provider for HttpClient!





**api.service.ts**

    import { Injectable } from &#39;@angular/core&#39;;
    import { HttpClient } from &#39;@angular/common/http&#39;;
    
    @Injectable()
    export class ApiService {
    
      constructor(private http: HttpClient) { }
      url = &#39;./assets/data.json&#39;;
    
      get() {
        return this.http.get(this.url);
      }
    }


**api.service.spec.ts**

    import { TestBed, inject } from &#39;@angular/core/testing&#39;;
    import { HttpClientTestingModule, HttpTestingController } from &#39;@angular/common/http/testing&#39;;
    
    import { ApiService } from &#39;./api.service&#39;;
    
    describe(&#39;ApiService&#39;, () =&gt; {
      beforeEach(() =&gt; {
        TestBed.configureTestingModule({
          imports: [
            HttpClientTestingModule,
          ],
          providers: [
            ApiService,
          ],
        });
      });
    
      it(&#39;should get users&#39;, inject([HttpTestingController, ApiService],
          (httpMock: HttpTestingController, apiService: ApiService) =&gt; {
            expect(apiService).toBeTruthy();
          }
        )
      );
    });


I don&#39;t understand what is going wrong as I have included HttpClient into api.service.ts, the service works in the browser.

This is directly called in a component called MapComponent, and that is called inside HomeComponent.



    Chrome 63.0.3239 (Mac OS X 10.13.3) HomeComponent expect opened to be false FAILED
    	Error: StaticInjectorError(DynamicTestModule)[ApiService -&gt; HttpClient]: 
    	  StaticInjectorError(Platform: core)[ApiService -&gt; HttpClient]: 
    	    NullInjectorError: No provider for HttpClient!



Angular 5 service failing to pass unit tests with (NullInjectorError: No provider for HttpClient!)

I&#39;ve found myself in an almost endless cycle of errors when trying to update my Angular CLI and NPM. Every time I update, I am met with WARN messages telling me to install peer dependencies (see below), but each time I install a dependency, I am met with more WARN messages. Is there a better way of handling this situation or does it seriously take hours?

    npm WARN @angular/animations@5.2.1 requires a peer of @angular/core@5.2.1 
    but none is installed. You must install peer dependencies yourself.
    npm WARN @angular/compiler-cli@5.1.0 requires a peer of typescript@&gt;=2.4.2 
    &lt;2.6 but none is installed. You must install peer dependencies yourself.
    npm WARN @ng-bootstrap/ng-bootstrap@1.0.0-beta.6 requires a peer of 
    @angular/core@^4.0.3 but none is installed. You must install peer 
    dependencies yourself.
    npm WARN @ng-bootstrap/ng-bootstrap@1.0.0-beta.6 requires a peer of 
    @angular/common@^4.0.3 but none is installed. You must install peer 
    dependencies yourself.
    npm WARN @ng-bootstrap/ng-bootstrap@1.0.0-beta.6 requires a peer of 
    @angular/forms@^4.0.3 but none is installed. You must install peer 
    dependencies yourself.
    npm WARN @schematics/angular@0.1.17 requires a peer of @angular-
    devkit/core@0.0.29 but none is installed. You must install peer dependencies 
    yourself.
    npm WARN @schematics/angular@0.1.17 requires a peer of @angular-
    devkit/schematics@0.0.52 but none is installed. You must install peer 
    dependencies yourself.
    npm WARN @schematics/schematics@0.0.11 requires a peer of @angular-
    devkit/core@0.0.22 but none is installed. You must install peer dependencies 
    yourself.
    npm WARN angular2-notifications@0.7.4 requires a peer of 
    @angular/core@^4.0.1 but none is installed. You must install peer 
    dependencies yourself.
    npm WARN angular2-notifications@0.7.4 requires a peer of 
    @angular/common@^4.0.1 but none is installed. You must install peer 
    dependencies yourself.
    npm WARN angular2-notifications@0.7.4 requires a peer of @angular/platform-
    browser@^4.0.0 but none is installed. You must install peer dependencies 
    yourself.
    npm WARN angular2-notifications@0.7.4 requires a peer of 
    @angular/animations@^4.0.1 but none is installed. You must install peer 
    dependencies yourself.
    npm WARN bootstrap@4.0.0-beta.2 requires a peer of jquery@1.9.1 - 3 but none 
    is installed. You must install peer dependencies yourself.
    npm WARN bootstrap@4.0.0-beta.2 requires a peer of popper.js@^1.12.3 but 
    none is installed. You must install peer dependencies yourself.
    npm WARN ng2-toasty@4.0.3 requires a peer of @angular/core@^2.4.7 || ^4.0.0 
    but none is installed. You must install peer dependencies yourself.
    npm WARN ngx-carousel@1.3.5 requires a peer of @angular/core@^2.4.0 || 
    ^4.0.0 but none is installed. You must install peer dependencies yourself.
    npm WARN ngx-carousel@1.3.5 requires a peer of @angular/common@^2.4.0 || 
    ^4.0.0 but none is installed. You must install peer dependencies yourself.
    npm WARN tsickle@0.25.5 requires a peer of typescript@&gt;=2.4.2 &lt;2.6 but none 
    is installed. You must install peer dependencies yourself.
    npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.1.3 
    (node_modules\fsevents):
    npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for 
    fsevents@1.1.3: wanted {&quot;os&quot;:&quot;darwin&quot;,&quot;arch&quot;:&quot;any&quot;} (current: 
    {&quot;os&quot;:&quot;win32&quot;,&quot;arch&quot;:&quot;x64&quot;})

I know I must be doing something wrong, but I&#39;m new to Angular.




How do I deal with installing peer dependencies in Angular CLI?

I am using the `Angular-CLI 1.6.6` and `@angular/service-worker 5.2.5` in our `Angular 5.2.5` app. Everything works fine on the local lite-server, as well as on the production server, except for one error message popping in our production environment: 

&gt; Failed to load resource: the server responded with a status of 504
&gt; (Gateway Timeout)

Looking into the `ngsw-worker.js` script I found the lines (2466 following) where the error message above is generated:

```typescript
    async safeFetch(req) {
        try {
            return await this.scope.fetch(req);
        }
        catch (err) {
            this.debugger.log(err, `Driver.fetch(${req.url})`);
            return this.adapter.newResponse(null, {
                status: 504,
                statusText: &#39;Gateway Timeout&#39;,
            });
        }
    } 
```
Console logging err in the catch puts out the following error:
```bash
    TypeError: Failed to execute &#39;fetch&#39; on &#39;ServiceWorkerGlobalScope&#39;: &#39;only-if-cached&#39; can be set only with &#39;same-origin&#39; mode
        at Driver.safeFetch (ngsw-worker.js:2464)
        at Driver.handleFetch (ngsw-worker.js:1954)
        at &lt;anonymous&gt;
```
An error that seems related to this question: https://stackoverflow.com/questions/48463483/what-causes-a-failed-to-execute-fetch-on-serviceworkerglobalscope-only-if

The req that generates this error is any first access to the app:

    https://example.com/test/#/connect
    https://example.com/test/#/map?token=[accestoken]
    ...

On app reload the error is not repeated.

Can anybody help me out here? Is there a bug in `safeFetch()` of the service worker (maybe to support HashLocationStrategy)? Do I have to change anything in my config?

Angular Service Worker - Failed to load resource: the server responded with a status of 504 (Gateway Timeout)

Just want to learn how Angular builds and runs behind the scenes? 

Below is what I understood thus far. Want to know if I missed something.

**How Angular builds**

After coding our Angular apps using TypeScript, we use the Angular CLI command to build the app.

`ng build` command compiles the application into an output directory and the build artifacts will be stored in the `dist/` directory.


**Internal Process**

**1.** Angular CLI runs Webpack to build and bundle all JavaScript and CSS code.

**2.**  In turn Webpack calls the TypeScript loaders which fetches all `.ts` file in the Angular project and then transpiles them to JavaScript i.e to a `.js` file, which browsers can understand.


[This](https://stackoverflow.com/a/46671117/2218697) post says Angular has two compilers:

 - View Compiler
       
 - Module Compiler

**Questions on builds**

What is the sequence of calling the build process?

Angular CLI first calls Angular built-in compiler written in TypeScript =&gt; then calls the TypeScript Transpiler  =&gt;  then calls the Webpack to bundle and store in the `dist/` directory.


**How Angular runs**


When build is completed, all our app&#39;s components, services, modules etc are transpiled to `JavaScript .js` files which is used to run the Angular application in the browser. 


Statements in [Angular Docs](https://Angular.io/guide/displaying-data)


1. When you bootstrap with the `AppComponent` class (in main.ts), Angular looks for a `&lt;app-root&gt;` in the `index.html`, finds it, instantiates an instance of AppComponent, and renders it inside the `&lt;app-root&gt;` tag.


2. Angular creates, updates, and destroys components as the user moves through the application.

**Questions on runs**

Although `main.ts` is used in the statement above for explaining the bootstrap process, Isn&#39;t Angular app is bootstrapped or started using JavaScript `.js` files? 

Isn&#39;t all the above statements are done runtime using JavaScript `.js` files?


Does anyone know how all parts fit together in depth?

How Angular builds and runs

When I try to build my project running the following command:

&lt;!-- language-all: lang-none --&gt;
     
    ng build --environment=prod --aot=false  --output-path=&quot;...&quot; --base-href=&quot;...&quot;
You seem to not be depending on `@angular/core`.

This is an error, however, I don&#39;t understand why because before it worked well.

I tried to do this: 

&lt;!-- language-all: lang-none --&gt;

    npm install @angular/core 

But I get this error : 
    
&gt;`error     at Error (native)
error  { Error: EACCES: permission denied, chown &#39;&#39;
error     at Error (native)
error   errno: -13,
error   code: &#39;EACCES&#39;,
error   syscall: &#39;chown&#39;,
error Please try running this command again as root/Administrator.
verbose exit [ -13, true ]`

I also tried to get rid of `node_modules`, then make an install npm: but I get the same error.

And when I run the following command:

&lt;!-- language-all: lang-none --&gt;

    ng serve

I have another error:
                                                                                                            
&gt;`The &quot;@angular/compiler-cli&quot; package was not properly installed. Error: Error: Cannot find module &#39;@angular/compiler-cli&#39;`

This is my `package.json` :

&lt;!-- language-all: lang-json --&gt;

    &quot;ng&quot;: &quot;ng&quot;,
    &quot;start&quot;: &quot;ng serve&quot;,
    &quot;build&quot;: &quot;ng build&quot;,
    &quot;test&quot;: &quot;ng test&quot;,
    &quot;lint&quot;: &quot;ng lint&quot;,
    &quot;e2e&quot;: &quot;ng e2e&quot;
 
    &quot;@angular/animations&quot;: &quot;^4.0.0&quot;,
    &quot;@angular/common&quot;: &quot;^4.0.0&quot;,
    &quot;@angular/compiler&quot;: &quot;^4.0.0&quot;,
    &quot;@angular/core&quot;: &quot;^4.0.0&quot;,
    &quot;@angular/forms&quot;: &quot;^4.0.0&quot;,
    &quot;@angular/http&quot;: &quot;^4.0.0&quot;,
    &quot;@angular/platform-browser&quot;: &quot;^4.0.0&quot;,
    &quot;@angular/platform-browser-dynamic&quot;: &quot;^4.0.0&quot;,
    &quot;@angular/router&quot;: &quot;^4.0.0&quot;,
    &quot;@types/jquery&quot;: &quot;^3.2.17&quot;,
    &quot;cli-color&quot;: &quot;^1.2.0&quot;,
    &quot;core-js&quot;: &quot;^2.4.1&quot;,
    &quot;font-awesome&quot;: &quot;^4.7.0&quot;,
    &quot;jquery&quot;: &quot;^3.2.1&quot;,
    &quot;matrix-js-sdk&quot;: &quot;^0.8.5&quot;,
    &quot;moment&quot;: &quot;^2.18.1&quot;,
    &quot;olm&quot;: &quot;https://matrix.org/packages/npm/olm/olm-2.2.2.tgz&quot;,
    &quot;readline&quot;: &quot;^1.3.0&quot;,
    &quot;rxjs&quot;: &quot;^5.4.1&quot;,
    &quot;socket.io-client&quot;: &quot;^2.0.3&quot;,
    &quot;zone.js&quot;: &quot;^0.8.14&quot;
  
    &quot;@angular/cli&quot;: &quot;1.2.6&quot;,
    &quot;@angular/compiler-cli&quot;: &quot;^4.0.0&quot;,
    &quot;@angular/language-service&quot;: &quot;^4.0.0&quot;,
    &quot;@types/jasmine&quot;: &quot;~2.5.53&quot;,
    &quot;@types/jasminewd2&quot;: &quot;~2.0.2&quot;,
    &quot;@types/jquery&quot;: &quot;^3.2.17&quot;,
    &quot;@types/node&quot;: &quot;~6.0.60&quot;,
    &quot;codelyzer&quot;: &quot;~3.0.1&quot;,
    &quot;jasmine-core&quot;: &quot;~2.6.2&quot;,
    &quot;jasmine-spec-reporter&quot;: &quot;~4.1.0&quot;,
    &quot;karma&quot;: &quot;~1.7.0&quot;,
    &quot;karma-chrome-launcher&quot;: &quot;~2.1.1&quot;,
    &quot;karma-cli&quot;: &quot;~1.0.1&quot;,
    &quot;karma-coverage-istanbul-reporter&quot;: &quot;^1.2.1&quot;,
    &quot;karma-jasmine&quot;: &quot;~1.1.0&quot;,
    &quot;karma-jasmine-html-reporter&quot;: &quot;^0.2.2&quot;,
    &quot;protractor&quot;: &quot;~5.1.2&quot;,
    &quot;ts-node&quot;: &quot;~3.0.4&quot;,
    &quot;tslint&quot;: &quot;~5.3.2&quot;,
    &quot;typescript&quot;: &quot;~2.3.3&quot;



Content Type	Original Author	Original Content on Stackoverflow
Question	Praveen Ojha	View Question on Stackoverflow
Solution 1 - Angular	Sajeetharan	View Answer on Stackoverflow
Solution 2 - Angular	Mano	View Answer on Stackoverflow
Solution 3 - Angular	Krusha Shah	View Answer on Stackoverflow
Solution 4 - Angular	Kiran Lohar	View Answer on Stackoverflow

What is the use of polyfills.ts file in Angular

Angular Problem Overview

Angular Solutions

Solution 1 - Angular

Solution 2 - Angular

Solution 3 - Angular

Solution 4 - Angular

Return "raw" json in ASP.NET Core 2.0 Web Api

How to use Java 8 Optionals, performing an action if all three are present?

Attributions