Angular Interpolation Expression HTML Example

By Arvind Rai, October 02, 2021

This page will walk through Angular interpolation expression HTML example. Interpolation is represented using double-curly braces {{ }}. With Interpolation, we evaluate expressions in HTML template. Interpolation can also be used for data binding in HTML element.
Here on this page we will provide demo with two components i.e. news and math components. In news component, interpolation is executing component properties for news and math component is performing mathematical operations.

Technologies Used
Interpolation Expression
Complete Example
Run Application
Reference
Download Source Code

Technologies Used

Find the technologies being used in our example.
1. Angular 12.1.0
2. Node.js 12.14.1
3. NPM 7.20.3

Interpolation Expression

Angular uses double-curly braces {{ }} to represent interpolation. Interpolation executes expressions in HTML template. Suppose we want to do mathematical calculations, we can perform in HTML template as follows.

Sum of 20 + 30 is  {{20 + 30}}

And it prints as

Sum of 20 + 30 is  50

Interpolation accesses values of component properties. Find some examples.

{{title}}
{{primeMinister.name.lname}}

Interpolation can also be used to assign the values to HTML tag attributes.

<img src="{{imageUrl}}">

Complete Example

For the demo we are creating two components, one for news and second for mathematical calculation.

news.component.ts

import { Component } from '@angular/core';
@Component({
  selector: 'news-app',
  templateUrl: './news.component.html',
  styleUrls: ['./news.component.css']
})
export class NewsComponent {
  title = 'Latest News';
  city = 'Varanasi';
  primeMinister = {
    name: {
      fname: 'Narendra',
      lname: 'Modi'
    },
    gender: 'M'
  }
}

We have created title, city and primeMinister properties in our news component. These properties will be accessed in news.component.html. Find the HTML file.

news.component.html

<h1> {{title}} </h1>
<p> 
   The Prime Minister {{primeMinister.gender == 'M'? 'Mr.' : 'Ms.'}}  
   
   {{primeMinister.name.fname}} {{primeMinister.name.lname}} visited {{city}}.
</p>

Here we are evaluating component properties using interpolation. Interpolation can be used within HTML tags or without HTML tags. It can also be used for property binding. Now find the CSS used with news component.

news.component.css

h1 {
  color: #1F618D;
  font-family: Arial;
  font-size: 200%;
}
p {
  color: #424949;
  font-family: sans-serif;
  font-size: 100%;
}

Now find second component, HTML template and CSS file for mathematical calculations.

math.component.ts

import { Component } from '@angular/core';
@Component({
    selector: 'math-app',
    templateUrl: './math.component.html',
    styleUrls: ['./math.component.css']
})
export class MathComponent {
    title = 'Math Calculation';
}

math.component.html

<h2> {{title}} </h2>

Sum of 15 + 23 is {{15 + 23}} <br/>

Multiplication of 23 * 12 is {{23 * 12}}

math.component.css

h2 {
  color: #800000;
  font-family: Arial;
  font-size: 150%;
}

Find application component.
app.component.ts

import { Component } from '@angular/core';
@Component({
	selector: 'app-root',
	template: `
	            <news-app> </news-app>
		    <math-app> </math-app>					
		`
})
export class AppComponent { }

Here we are creating two tags <news-app> for news component and <math-app> for math component.
Now create application module.
app.module.ts

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { NewsComponent } from './news.component';
import { MathComponent } from './math.component';
import { AppComponent } from './app.component';
@NgModule({
  imports: [BrowserModule],
  declarations: [AppComponent, NewsComponent, MathComponent],
  bootstrap: [AppComponent]
})
export class AppModule { }

Run Application

To run the demo application, find the following steps.
1. Download source code using download link given below on this page.
2. Use downloaded src in your angular CLI application. To install angular CLI, find the link.
3. Run ng serve using command prompt.
4. Now access the URL http://localhost:4200