Styles cannot be applied to elements that are dynamically generated

Question

Styles cannot be applied to elements that are dynamically generated

I am currently working on a project in Angular 9.1.13, hosted on Centos 7.

One of the components in my project contains static HTML code, shown below:

<ul id="myUL">
   <li><span class="caret">Top 1</span>
      <ul class="nested">
         <li>Sub 1</li>
         <li>Sub 2</li>
      </ul>
   </li>
</ul>

The CSS styling for this component is as follows:

ul, #myUL {
  list-style-type: none;
}

#myUL {
  margin: 0;
  padding: 0;
}

.caret {
  cursor: pointer;
  user-select: none;
}

.caret::before {
  content: "\25B6";
  display: inline-block;
  margin-right: 6px;
}

.caret-down::before {
  transform: rotate(90deg);
}

.nested {
  display: none;
}

.active {
  display: block;
}

In the ngOnInit() method of the component, the following JavaScript code is executed:

...
const toggler = document.getElementsByClassName('caret');
let i;
     
for (i = 0; i < toggler.length; i++) {
   toggler[i].addEventListener('click', function() {
      this.parentElement.querySelector('.nested').classList.toggle('active');
      this.classList.toggle('caret-down');      
   });
}
...

Although everything works well with the pre-defined HTML structure, issues arise when trying to dynamically generate the list content.

To achieve dynamic content generation, the HTML structure is modified as follows:

<ul id="myUL"></ul> <!-- intentionally left empty -->

Prior to the mentioned code within the ngOnInit(), the following snippet is added:

...
const myUL = document.getElementById('myUL');

myUL.innerHTML = 
   '<li><span class="caret">Top 1</span><ul class="nested"><li>Sub 1</li><li>Sub 2</li></ul></li>';

// Continue executing the previous code
...

Trouble arises from the fact that the dynamic content does not retain collapsible functionality or proper styling, despite having click events properly attached to the relevant elements:

My goal is to dynamically generate the list while maintaining the same interactive behavior and style seen in the initial screenshot.

html css angular

Answer 1

Answer №1

Disclaimer: The following information is relevant only if you are specifically required to inject HTML as a string. For instance, when receiving the string from an API. In general, it is recommended to utilize Angular directives for generating content dynamically.

In Angular, View Encapsulation is implemented to ensure component-specific styling. This is achieved by assigning a unique identifier as an attribute to all HTML elements within the component, typically denoted as _ngcontent-nxs-c94="". Subsequently, this identifier is appended to CSS declarations within the component using [_ngcontent-nxs-c94]. By inspecting your elements, you can observe this process.

If HTML injection occurs post-compilation of the component, the injected HTML will not possess the unique attribute, resulting in unaffected CSS styles. While injecting HTML directly is discouraged due to Angular's dynamic content generation capabilities, should it be necessary, global CSS application (without the unique attribute) is recommended. Files specified in the styles array within angular.json are compiled as global styles, with styles.css serving as the default file.

To apply global styles, simply add your CSS to a file included in the styles array, such as styles.css, or create a new file adjacent to your original CSS file. However, caution must be exercised to ensure unique selectors, possibly by encapsulating all CSS within the component's HTML tag and incorporating additional unique class names for nested components to prevent unintended style conflicts.

Incorporating Global Styles into a Component

app-my-component {
  ul,
  #myUL {
    list-style-type: none;
  }

  #myUL {
    margin: 0;
    padding: 0;
  }

  .caret {
    cursor: pointer;
    user-select: none;
  }

  .caret::before {
    content: "\25B6";
    display: inline-block;
    margin-right: 6px;
  }

  .caret-down::before {
    transform: rotate(90deg);
  }

  .nested {
    display: none;
  }

  .active {
    display: block;
  }
}

This approach facilitates the application of global styles to a component while upholding view encapsulation within the original CSS file. Alternatively, disabling view encapsulation for the component is possible but not advisable, as it may inadvertently impact other components that require encapsulated styling.

Disabling View Encapsulation (not recommended)

@Component({
  selector: 'app-one',
  templateUrl: './one.component.html',
  styleUrls: ['./one.component.scss'],
  encapsulation: ViewEncapsulation.None
})
export class OneComponent {
  ...
}

By opting for this method, ./one.component.scss will be treated globally akin to files listed in the styles array. Before proceeding with this approach, ensure that the CSS modifications do not adversely affect other components.

Answer 2

Disclaimer: The following information is relevant only if you are specifically required to inject HTML as a string. For instance, when receiving the string from an API. In general, it is recommended to utilize Angular directives for generating content dynamically.

In Angular, View Encapsulation is implemented to ensure component-specific styling. This is achieved by assigning a unique identifier as an attribute to all HTML elements within the component, typically denoted as _ngcontent-nxs-c94="". Subsequently, this identifier is appended to CSS declarations within the component using [_ngcontent-nxs-c94]. By inspecting your elements, you can observe this process.

If HTML injection occurs post-compilation of the component, the injected HTML will not possess the unique attribute, resulting in unaffected CSS styles. While injecting HTML directly is discouraged due to Angular's dynamic content generation capabilities, should it be necessary, global CSS application (without the unique attribute) is recommended. Files specified in the styles array within angular.json are compiled as global styles, with styles.css serving as the default file.

To apply global styles, simply add your CSS to a file included in the styles array, such as styles.css, or create a new file adjacent to your original CSS file. However, caution must be exercised to ensure unique selectors, possibly by encapsulating all CSS within the component's HTML tag and incorporating additional unique class names for nested components to prevent unintended style conflicts.

Incorporating Global Styles into a Component

app-my-component {
  ul,
  #myUL {
    list-style-type: none;
  }

  #myUL {
    margin: 0;
    padding: 0;
  }

  .caret {
    cursor: pointer;
    user-select: none;
  }

  .caret::before {
    content: "\25B6";
    display: inline-block;
    margin-right: 6px;
  }

  .caret-down::before {
    transform: rotate(90deg);
  }

  .nested {
    display: none;
  }

  .active {
    display: block;
  }
}

This approach facilitates the application of global styles to a component while upholding view encapsulation within the original CSS file. Alternatively, disabling view encapsulation for the component is possible but not advisable, as it may inadvertently impact other components that require encapsulated styling.

Disabling View Encapsulation (not recommended)

@Component({
  selector: 'app-one',
  templateUrl: './one.component.html',
  styleUrls: ['./one.component.scss'],
  encapsulation: ViewEncapsulation.None
})
export class OneComponent {
  ...
}

By opting for this method, ./one.component.scss will be treated globally akin to files listed in the styles array. Before proceeding with this approach, ensure that the CSS modifications do not adversely affect other components.

Answer 3

Answer №2

To ensure proper styling for custom elements, it is recommended to utilize ng-deep and turn off scoped styles.

#myUL ::ng-deep {
  .caret {
    cursor: pointer;
    user-select: none;
  }

  .caret::before {
    content: "\25B6";
    display: inline-block;
    margin-right: 6px;
  }

  .caret-down::before {
    transform: rotate(90deg);
  }

  .nested {
    display: none;
  }

  .active {
    display: block;
  } 

}

Answer 4

To ensure proper styling for custom elements, it is recommended to utilize ng-deep and turn off scoped styles.

#myUL ::ng-deep {
  .caret {
    cursor: pointer;
    user-select: none;
  }

  .caret::before {
    content: "\25B6";
    display: inline-block;
    margin-right: 6px;
  }

  .caret-down::before {
    transform: rotate(90deg);
  }

  .nested {
    display: none;
  }

  .active {
    display: block;
  } 

}

Answer 5

Answer №3

If you want to create a dynamic list in your HTML using Angular, you can set up a caret object/list in your component and utilize *ngFor and [ngClass] to achieve the desired functionality. Here's an example:

component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.scss'],
})
export class AppComponent {
  carets = [
    {
      name: 'Top 1',
      children: [{ name: 'Sub 1' }, { name: 'Sub 2' }],
      toggle: false,
    },
    {
      name: 'Top 2',
      children: [{ name: 'Sub 1' }, { name: 'Sub 2' }],
      toggle: false,
    },
  ];
}

component.html

<ul id="myUL">
  <li *ngFor="let caret of carets" [ngClass]="caret.toggle ? 'active' : ''" >
    <span
      class="caret"
      [ngClass]="caret.toggle ? 'caret-down' : ''"
      (click)="caret.toggle = !caret.toggle"
      >{{ caret.name }}</span
    >
    <ul [ngClass]="caret.toggle ? '' : 'nested'">
      <li *ngFor="let child of caret.children">{{ child.name }}</li>
    </ul>
  </li>
</ul>

Answer 6

If you want to create a dynamic list in your HTML using Angular, you can set up a caret object/list in your component and utilize *ngFor and [ngClass] to achieve the desired functionality. Here's an example:

component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.scss'],
})
export class AppComponent {
  carets = [
    {
      name: 'Top 1',
      children: [{ name: 'Sub 1' }, { name: 'Sub 2' }],
      toggle: false,
    },
    {
      name: 'Top 2',
      children: [{ name: 'Sub 1' }, { name: 'Sub 2' }],
      toggle: false,
    },
  ];
}

component.html

<ul id="myUL">
  <li *ngFor="let caret of carets" [ngClass]="caret.toggle ? 'active' : ''" >
    <span
      class="caret"
      [ngClass]="caret.toggle ? 'caret-down' : ''"
      (click)="caret.toggle = !caret.toggle"
      >{{ caret.name }}</span
    >
    <ul [ngClass]="caret.toggle ? '' : 'nested'">
      <li *ngFor="let child of caret.children">{{ child.name }}</li>
    </ul>
  </li>
</ul>

Styles cannot be applied to elements that are dynamically generated

Answer №1

Answer №2

Answer №3

component.ts

component.html

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