Angular Add Class Dynamically

Angular Add Class Dynamically

Is there a way to add a class from the .ts file, using Angular solutions

<div [class.extra-sparkle]="isDelightful == true">

I want to do the above but from the side of the .ts file. The less code the better.

<button class="general" (click)="ChangeScreen('Global')"       [class.selected]="CurrentPage == 'Global'">Global</button>
<button class="general" (click)="ChangeScreen('Maintenance')"  [class.selected]="CurrentPage == 'Maintenance'">Maintenance</button>
<button class="general" (click)="ChangeScreen('Settings')"     [class.selected]="CurrentPage == 'Settings'">Settings</button>
<button class="general" (click)="ChangeScreen('Profile')"      [class.selected]="CurrentPage == 'Profile'">Profile</button>
<button class="general" (click)="ChangeScreen('Transactions')" [class.selected]="CurrentPage == 'Transactions'">Transactions</button>

I would like to just add something like this into the ChangeScreen function:

ChangeScreen(page) {
    page.addClass = page;
}

Then I can remove all of those lines: [class.selected]="CurrentPage == '...'"

2

3 Answers

You can use ngClass directive:

<div id="mydiv" [ngClass]="{'myCSSclass' : condition}"></div>

Simple as that! myDiv will have the class myCSSclass only when the condition evaluates to true. This condition can be set in your typescript file or in the template.

1

Use Renderer

See here:

and here:

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

constructor(private render:Renderer) { }

ChangeScreen(event:any) {
 this.renderer.setElementClass(event.target,"selected",true);
}

In html:

<button class="general" (click)="ChangeScreen()">Global</button>

Or Render2:

See here:

and here:

import { Renderer2 } from '@angular/core';

constructor(private render:Renderer2) { }

ChangeScreen(event:any) {
 this.renderer.addClass(event.target,"selected");
}

In html:

<button class="general" (click)="ChangeScreen($event)">Global</button>
9

While the solution with the Renderer works, I am proposing you create a data structure for your buttons

buttons: Array<{label: string}> = [
    {
      label: 'Global'
    },
    {
      label: 'Maintenance'
    },
    {
      label: 'Settings'
    },
    {
      label: 'Profile'
    },
    {
      label: 'Transactions'
    }
  ]

This can easily be iterated through using ngFor

<button 
  *ngFor="let button of buttons" 
  class="general" 
  (click)="ChangeScreen(button.label)" 
  [class.selected]="CurrentPage == button.label">
  {{ button.label }}
</button>

And only thing your ChangeScreen method would need is... the thing its already doing, setting the current page!

See stackblitz for an example of how this plays out.

1

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James H. Sterling
Author

James H. Sterling

James Sterling reports on renewable energy developments, climate policy, ecological conservation, and green tech innovations around the globe.