NgLet

Angular structural directive for sharing data as local variable into html component template.

Description

Sometime there is a need to share data into component template as local variable. This structural directive create local context of variable that can be used into html template.

See the stackblitz demo.

Features

✅ Observable support
✅ Async pipe support
✅ NgModel support
✅ Type casting

Get Started

Step 1: install ng-let

npm i ng-let

Step 2: Import NgLetModule into your app module, eg.:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';

import { NgLetModule } from 'ng-let';

@NgModule({
  declarations: [AppComponent],
  imports: [
    BrowserModule,
    NgLetModule,
  ],
  providers: [],
  bootstrap: [AppComponent],
  ],
})
export class AppModule { }

Step 3: usage, eg.:

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

@Component({
  selector: 'app-root',
  template: `
  <ng-container *ngLet="(num1 + num2) as total"> <!-- single computation -->
    <div>
      1: {{ total }} <!-- 3 -->
    </div>
    <div>
      2: {{ total }} <!-- 3 -->
    </div>
  </ng-container> 
  `,
})
export class AppComponent {
  num1: number = 1;
  num2: number = 2;
}

or with the implicit syntax:

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

@Component({
  selector: 'app-root',
  template: `
  <ng-container *ngLet="(num1 + num2); let total"> <!-- single computation -->
    <div>
      1: {{ total }} <!-- 3 -->
    </div>
    <div>
      2: {{ total }} <!-- 3 -->
    </div>
  </ng-container> 
  `,
})
export class AppComponent {
  num1: number = 1;
  num2: number = 2;
}

Examples

Below there are some examples of use case.

Example: observable

Example of use with observable, eg.:

import { Component } from '@angular/core';
import { defer, Observable, timer } from 'rxjs';

@Component({
  selector: 'app-root',
  template: `
  <ng-container *ngLet="timer$ | async as time"> <!-- single subscription -->
    <div>
      1: {{ time }}
    </div>
    <div>
      2: {{ time }}
    </div>
  </ng-container>
  `,
})
export class AppComponent {
  timer$: Observable<number> = defer(() => timer(3000, 1000));
}

or with the implicit syntax:

import { Component } from '@angular/core';
import { defer, Observable, timer } from 'rxjs';

@Component({
  selector: 'app-root',
  template: `
  <ng-container *ngLet="timer$ | async; let time"> <!-- single subscription -->
    <div>
      1: {{ time }}
    </div>
    <div>
      2: {{ time }}
    </div>
  </ng-container>
  `,
})
export class AppComponent {
  timer$: Observable<number> = defer(() => timer(3000, 1000));
}

Example: signal

Example of use with signal, eg.:

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

@Component({
  selector: 'app-root',
  template: `
  <ng-container *ngLet="mySignal() as time"> <!-- single computation -->
    <div>
      1: {{ time }}
    </div>
    <div>
      2: {{ time }}
    </div>
  </ng-container>
  `,
})
export class AppComponent {
  mySignal = signal(1);

  constructor() {
    setInterval(() => this.mySignal.update(value => value + 1), 1000)
  }
}

or with the implicit syntax:

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

@Component({
  selector: 'app-root',
  template: `
  <ng-container *ngLet="mySignal(); let time"> <!-- single computation -->
    <div>
      1: {{ time }}
    </div>
    <div>
      2: {{ time }}
    </div>
  </ng-container>
  `,
})
export class AppComponent {
  mySignal = signal(1);

  constructor() {
    setInterval(() => this.mySignal.update(value => value + 1), 1000)
  }
}

Support

This is an open-source project. Star this repository, if you like it, or even donate. Thank you so much!

My other libraries

I have published some other Angular libraries, take a look:

• NgSimpleState: Simple state management in Angular with only Services and RxJS
• NgHttpCaching: Cache for HTTP requests in Angular application
• NgGenericPipe: Generic pipe for Angular application for use a component method into component template.
• NgForTrackByProperty: Angular global trackBy property directive with strict type checking