How and where to use ng-deep

Question

I m new to Angular 4  so could anyone please explain how and where to use   ng-deep in Angular 4  Actually I want to overwrite some of the CSS properties of the child components from the parent components  Moreover is it supported on IE11  Thanks for the help

User · Answer

Use   ng-deep with caution   I used it throughout my app to set the material design toolbar color to different colors throughout my app only to find that when the app was in testing the toolbar colors step on each other   Come to find out it is because these styles becomes global  see this article  Here is a working code solution that doesn t bleed into other components   lt mat-toolbar  subbar gt       lt  mat-toolbar gt   export class BypartSubBarComponent implements AfterViewInit      ViewChild  subbar     static  false    subbar  MatToolbar    constructor      private renderer  Renderer2        ngAfterViewInit         this renderer setStyle        this subbar  elementRef nativeElement   backgroundColor    red

User · Answer

I would emphasize the importance of limiting the   ng-deep to only children of a component by requiring the parent to be an encapsulated css class  For this to work it s important to use the   ng-deep after the parent  not before otherwise it would apply to all the classes with the same name the moment the component is loaded  Using the  host keyword before   ng-deep will handle this automatically   host   ng-deep  mat-checkbox-layout   Alternatively you can achieve the same behavior by adding a component scoped CSS class before the   ng-deep keyword   my-component   ng-deep  mat-checkbox-layout       background-color  aqua     Component template   lt h1 class  quot my-component quot  gt       lt mat-checkbox      gt  lt  mat-checkbox gt   lt  h1 gt    Resulting  Angular generated  css will then include the uniquely generated name and apply only to its own component instance   my-component  ngcontent-c1   mat-checkbox-layout       background-color  aqua

User · Answer

Usually   deep     shadow-piercing    combinator  can be used to force a style down to child components  This selector had an alias  gt  gt  gt  and now has another one called   ng-deep  since  deep  combinator has been deprecated   it is recommended to use   ng-deep For example   lt div class  quot overview tab-pane quot  id  quot overview quot  role  quot tabpanel quot   innerHTML   quot project  getContent   DETAILS   quot  gt  lt  div gt   and css  overview         ng-deep           p                amp  last-child                   margin-bottom  0                                   it will be applied to child components

User · Answer

Make sure not to miss the explanation of  host-context which is directly above   ng-deep in the angular guide   https   angular io guide component-styles  I missed it up until now and wish I d seen it sooner    ng-deep is often necessary when you didn t write the component and don t have access to its source  but  host-context can be a very useful option when you do  For example I have a black  lt h1 gt  header inside a component I designed  and I want the ability to change it to white when it s displayed on a dark themed background  If I didn t have access to the source I may have to do this in the css for the parent   theme-dark widget-box   ng-deep h1   color  white     But instead with  host-context you can do this inside the component   h1          color  black           default color        host-context  theme-dark   amp                  color  white       color for dark-theme                 OR set an attribute  outside  with  attr theme   quot  dark  quot         host-context  theme  dark     amp                  color  white       color for dark-theme            This will look anywhere in the component chain for  theme-dark and apply the css to the h1 if found  This is a good alternative to relying too much on   ng-deep which while often necessary is somewhat of an anti-pattern  In this case the  amp  is replaced by the h1  that s how sass scss works  so you can define your  normal  and themed alternative css right next to each other which is very handy  Be careful to get the correct number of    For   ng-deep there are two and for  host-context only one

User · Answer

USAGE    ng-deep   gt  gt  gt  and  deep  disable view encapsulation for specific CSS rules  in other words  it gives you access to DOM elements  which are not in your component s HTML  For example  if you re using Angular Material  or any other third-party library like this   some generated elements are outside of your component s area  such as dialog  and you can t access those elements directly or using a regular CSS way  If you want to change the styles of those elements  you can use one of those three things  for example     ng-deep  mat-dialog        styles here        For now Angular team recommends making  deep  manipulations only with EMULATED view encapsulation   DEPRECATION   deep  manipulations are actually deprecated too  BUT it stills working for now  because Angular does pre-processing support  don t rush to refuse   ng-deep today  take a look at deprecation practices first    Anyway  before following this way  I recommend you to take a look at disabling view encapsulation approach  which is not ideal too  it allows your styles to leak into other components   but in some cases  it s a better way  If you decided to disable view encapsulation  it s strongly recommended to use specific classes to avoid CSS rules intersection  and finally  avoid a mess in your stylesheets  It s really easy to disable right in the component s  ts file    Component     selector        template        styles          encapsulation  ViewEncapsulation None     Use to disable CSS Encapsulation for this component      You can find more info about the view encapsulation in this article

User · Answer

Just an update    You should use   ng-deep instead of  deep  which seems to be deprecated   Per documentation      The shadow-piercing descendant combinator is deprecated and support is   being removed from major browsers and tools  As such we plan to drop   support in Angular  for all 3 of  deep       and   ng-deep   Until   then   ng-deep should be preferred for a broader compatibility with   the tools    You can find it here

[css] How and where to use ::ng-deep?

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