Questions tagged [angular]
Questions about Angular (not to be confused with AngularJS), the web framework from Google. Use this tag for Angular questions which are not specific to an individual version. For the older AngularJS (1.x) web framework, use the AngularJS tag.
300,123
questions
2072
votes
49
answers
1.6m
views
Can't bind to 'ngModel' since it isn't a known property of 'input'
I have this simple input in my component which uses [(ngModel)] :
<input type="text" [(ngModel)]="test" placeholder="foo" />
And I get the following error when I ...
- 60.7k
1851
votes
34
answers
806k
views
What is the difference between Promises and Observables?
What is the difference between Promise and Observable in Angular?
An example on each would be helpful in understanding both the cases. In what scenario can we use each case?
- 18.6k
1471
votes
27
answers
809k
views
Difference between Constructor and ngOnInit
Angular provides life cycle hook ngOnInit by default.
Why should ngOnInit be used, if we already have a constructor?
- 16.9k
1303
votes
50
answers
1.4m
views
Can't bind to 'formGroup' since it isn't a known property of 'form'
The situation
I am trying to make what should be a very simple form in my Angular application, but no matter what, it never works.
The Angular version
Angular 2.0.0 RC5
The error
Can't bind to '...
- 20.8k
1165
votes
24
answers
1.9m
views
Angular: conditional class with *ngClass
What is wrong with my Angular code? I am getting the following error:
Cannot read property 'remove' of undefined at BrowserDomAdapter.removeClass
<ol>
<li *ngClass="{active: step==='...
- 34.3k
1083
votes
24
answers
740k
views
Angular HTML binding
I am writing an Angular application and I have an HTML response I want to display.
How do I do that? If I simply use the binding syntax {{myVal}} it encodes all HTML characters (of course).
I need ...
- 32.1k
1021
votes
29
answers
392k
views
Angular/RxJS When should I unsubscribe from `Subscription`
When should I store the Subscription instances and invoke unsubscribe() during the ngOnDestroy life cycle and when can I simply ignore them?
Saving all subscriptions introduces a lot of mess into ...
- 12.1k
1011
votes
14
answers
648k
views
What is the difference between BehaviorSubject and Observable?
I'm looking into the design patterns of RxJS, and I do not understand the difference between BehaviorSubject and Observable.
From my understanding, BehaviorSubject can contain a value that may change. ...
- 10.2k
977
votes
22
answers
1.3m
views
How can I use "*ngIf else"?
I'm using Angular and I want to use *ngIf else (available since version 4) in this example:
<div *ngIf="isValid">
content here ...
</div>
<div *ngIf="!isValid">...
- 35.9k
895
votes
10
answers
1.6m
views
ngFor with index as value in attribute
I have a simple ngFor loop which also keeps track of the current index. I want to store that index value in an attribute so I can print it. But I can't figure out how this works.
I basically have ...
- 20.1k
883
votes
47
answers
1.7m
views
Angular 6 - Could not find module "@angular-devkit/build-angular"
After updating to Angular 6.0.1, I get the following error on ng serve:
Could not find module "@angular-devkit/build-angular" from "/home/Projects/myProjectName".
Error: Could not find module "@...
- 17.4k
875
votes
37
answers
1.2m
views
Property '...' has no initializer and is not definitely assigned in the constructor
in my Angular app i have a component:
import { MakeService } from './../../services/make.service';
import { Component, OnInit } from '@angular/core';
@Component({
selector: 'app-vehicle-form',
...
- 9,211
837
votes
20
answers
622k
views
How to detect when an @Input() value changes in Angular?
I have a parent component (CategoryComponent), a child component (videoListComponent) and an ApiService.
I have most of this working fine i.e. each component can access the json api and get its ...
- 11.9k
747
votes
41
answers
1.1m
views
How to get current route
The current docs only talk about getting route params, not the actual route segments.
For example, if i want to find the parent of current route, how is that possible?
- 43.7k
739
votes
23
answers
835k
views
What is the equivalent of ngShow and ngHide in Angular 2+?
I have a number of elements that I want to be visible under certain conditions.
In AngularJS I would write
<div ng-show="myVar">stuff</div>
How can I do this in Angular 2+?
- 12.3k
727
votes
15
answers
942k
views
How can I select an element in a component template?
Does anybody know how to get hold of an element defined in a component template? Polymer makes it really easy with the $ and $$.
I was just wondering how to go about it in Angular.
Take the example ...
- 7,893
708
votes
34
answers
1.4m
views
Unable to resolve dependency tree error when installing npm packages
When trying to install the npm packages using npm i command, I am getting the following exception:
I have tried reinstalling the Node.js package and setting the proxy to off using:
set HTTP_PROXY=
...
- 8,423
707
votes
25
answers
868k
views
No provider for HttpClient
After upgrading from angular 4.4 to 5.0 and after updating all HttpModule and Http to HttpClientModule I started to get this error.
I also added HttpModule again to be sure it's not due to some ...
- 7,131
667
votes
21
answers
729k
views
access key and value of object using *ngFor
I am a bit confused about how to get the key and value of an object in angular2 while using *ngFor for iterating over the object. I know in angular 1.x there is a syntax like
ng-repeat="(key, value) ...
- 84.2k
657
votes
32
answers
705k
views
How to detect a route change in Angular?
I am looking to detect a route change in my AppComponent.
Thereafter I will check the global user token to see if the user is logged in so that I can redirect the user if the user is not logged in.
- 16k
646
votes
14
answers
65k
views
Huge number of files generated for every Angular project
I wanted to start a simple hello world app for Angular.
When I followed the instructions in the official quickstart the installation created 32,000 files in my project.
I figured this is some ...
- 15.5k
637
votes
18
answers
468k
views
*ngIf and *ngFor on same element causing error
I'm having a problem with trying to use Angular's *ngFor and *ngIf on the same element.
When trying to loop through the collection in the *ngFor, the collection is seen as null and consequently ...
- 12k
632
votes
4
answers
105k
views
What is the meaning of the "at" (@) prefix on npm packages?
In the Angular Component Router documentation I just stumbled over a npm command I have never seen before and I don't understand what is going on:
npm install @angular/router --save
What is the ...
- 17.6k
576
votes
29
answers
574k
views
How to go back last page
Is there a smart way to go back last page in Angular 2?
Something like
this._router.navigate(LASTPAGE);
For example, page C has a Go Back button,
Page A -> Page C, click it, back to page A.
Page B ...
- 45.5k
573
votes
5
answers
462k
views
WARNING in budgets, maximum exceeded for initial
When building my Angular 7 project with --prod, I receive a warning in budgets.
I have an Angular 7 project. I am trying to build it, but I keep getting the following warning:
WARNING in budgets, ...
- 7,011
560
votes
24
answers
593k
views
Error: More than one module matches. Use skip-import option to skip importing the component into the closest module
When I try to create a component in the angular cli, it's showing me this error. How do I get rid of it ?
Error: More than one module matches. Use skip-import option to skip importing the component ...
- 7,109
560
votes
31
answers
492k
views
ExpressionChangedAfterItHasBeenCheckedError Explained
Please explain to me why I keep getting this error: ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked.
Obviously, I only get it in dev mode, it doesn't happen ...
- 8,182
550
votes
28
answers
737k
views
how to reset <input type = "file"> in Angular
I am developing a metro app with VS2012 and Javascript
I want to reset the contents of my file input:
<input type="file" id="uploadCaptureInputFile" class="win-content colors" accept="image/*" /&...
- 8,466
550
votes
12
answers
165k
views
@Directive vs @Component in Angular
What is the difference between @Component and @Directive in Angular?
Both of them seem to do the same task and have the same attributes.
What are the use cases and when to prefer one over another?
- 5,914
546
votes
11
answers
351k
views
Can't bind to 'formControl' since it isn't a known property of 'input' - Angular2 Material Autocomplete issue
I am trying to use Angular Material Autocomplete component in my Angular 2 project. I added the following to my template.
<md-input-container>
<input mdInput placeholder="Category" [...
- 22.4k
536
votes
16
answers
692k
views
Binding select element to object in Angular
I'd like to bind a select element to a list of objects -- which is easy enough:
@Component({
selector: 'myApp',
template:
`<h1>My Application</h1>
<select [(ngModel)]...
- 10.5k
518
votes
6
answers
196k
views
What is the difference between declarations, providers, and import in NgModule?
I am trying to understand Angular (sometimes called Angular2+), then I came across @Module:
Imports
Declarations
Providers
Following Angular Quick Start
- 7,331
510
votes
14
answers
843k
views
How can I get new selection in "select" in Angular 2?
I am using Angular 2 (TypeScript).
I want to do something with the new selection, but what I get in onChange() is always the last selection. How can I get the new selection?
<select [(ngModel)]="...
- 45.5k
507
votes
49
answers
466k
views
Error when trying to inject a service into an angular component "EXCEPTION: Can't resolve all parameters for component", why?
I've built a basic app in Angular, but I have encountered a strange issue where I cannot inject a service into one of my components. It injects fine into any of the three other components I have ...
- 5,128
502
votes
6
answers
1.0m
views
(change) vs (ngModelChange) in angular
Angular 1 does not accept onchange() event, it's only accepts ng-change() event.
Angular 2, on the other hand, accepts both (change) and (ngModelChange) events, which both seems to be doing the same ...
- 37.5k
488
votes
4
answers
388k
views
Triggering change detection manually in Angular
I'm writing an Angular component that has a property Mode(): string.
I would like to be able to set this property programmatically not in response to any event.
The problem is that in the absence of ...
- 9,229
483
votes
12
answers
207k
views
Angular exception: Can't bind to 'ngForIn' since it isn't a known native property
What am I doing wrong?
import {bootstrap, Component} from 'angular2/angular2'
@Component({
selector: 'conf-talks',
template: `<div *ngFor="let talk in talks">
{{talk.title}} by {{talk....
- 362k
480
votes
43
answers
690k
views
mat-form-field must contain a MatFormFieldControl
We are trying to build our own form-field-Components at our Company. We are trying to wrap material design's Components like this:
field:
<mat-form-field>
<ng-content></ng-content&...
- 5,687
477
votes
28
answers
269k
views
Angular 2 Scroll to top on Route Change
In my Angular 2 app when I scroll down a page and click the link at the bottom of the page, it does change the route and takes me to the next page but it doesn't scroll to the top of the page. As a ...
- 10.1k
454
votes
9
answers
360k
views
Angular - Use pipes in services and components
In AngularJS, I am able to use filters (pipes) inside of services and controllers using syntax similar to this:
$filter('date')(myDate, 'yyyy-MM-dd');
Is it possible to use pipes in services/...
- 4,663
441
votes
23
answers
473k
views
Expression ___ has changed after it was checked
Why is the component in this simple plunk
@Component({
selector: 'my-app',
template: `<div>I'm {{message}} </div>`,
})
export class App {
message:string = 'loading :(';
...
- 31.6k
438
votes
10
answers
295k
views
What is the difference between Subject and BehaviorSubject?
I'm not clear on the difference between a Subject and a BehaviorSubject. Is it just that a BehaviorSubject has the getValue() function?
- 9,591
418
votes
13
answers
737k
views
Angular 2 change event on every keypress
The change event is only called after the focus of the input has changed. How can I make it so that the event fires on every keypress?
<input type="text" [(ngModel)]="mymodel" (change)="...
- 34.3k
417
votes
3
answers
527k
views
Can't bind to 'ngIf' since it isn't a known property of 'div' [duplicate]
Can't bind to 'ngIf' since it isn't a known property of 'div'.
The element is <div [ngIf]="isAuth" id="sidebar">
And the component is:
import SessionService from '../session/...
- 4,353
416
votes
20
answers
834k
views
How do I pass data to Angular routed components?
In one of my Angular 2 routes's templates (FirstComponent) I have a button
first.component.html
<div class="button" click="routeWithData()">Pass data and route</div>
My goal is to ...
- 14.7k
412
votes
26
answers
620k
views
How to use jQuery with Angular?
Can anyone tell me, how to use jQuery with Angular?
class MyComponent {
constructor() {
// how to query the DOM element from here?
}
}
I'm aware there are workarounds like ...
- 7,147
411
votes
19
answers
440k
views
Property 'value' does not exist on type 'EventTarget'
I am using TypeScript Version 2 for an Angular 2 component code.
I am getting error "Property 'value' does not exist on type 'EventTarget'" for below code, what could be the solution. Thanks!...
- 10.2k
411
votes
16
answers
666k
views
npm WARN ... requires a peer of ... but none is installed. You must install peer dependencies yourself
I tried to run a project downloaded from github. Unfortunately, during npm install the following warnings were shown. I tried to change the version based on this question. However, I had a problem, ...
user7304253
406
votes
22
answers
395k
views
How to style child components from parent component's CSS file?
I've got a parent component:
<parent></parent>
And I want to populate this group with child components:
<parent>
<child></child>
<child></child>
<...
- 27.1k
405
votes
9
answers
341k
views
Convert Promise to Observable
I am trying to wrap my head around observables. I love the way observables solve development and readability issues. As I read, benefits are immense.
Observables on HTTP and collections seem to be ...
- 5,057