Interpolation vs. Property Binding in Angular

Angular, a powerful front-end framework, offers various techniques to dynamically update and display data in your applications. Two commonly used methods for this purpose are interpolation and property binding.

In this article, we will learn about interpolation and property binding and also see the key differences between them.

Interpolation

Interpolation is a one-way data binding technique in Angular that allows you to embed expressions within double curly braces {{ }} directly in the HTML template. The expression is evaluated and the result is converted to a string, which is then rendered in the view.

Syntax of interpolation:

<p>{{ expression }}</p>

Features of Interpolation:

• Simple syntax for embedding dynamic values.
• Automatic data conversion to string.
• Ideal for displaying data in templates.

Example of Interpolation:

Step 1: Create Angular Project using the following command.

ng new interpolation-example
cd interpolation-example

Step 2: Create a component ‘welcome’ using the following command.

ng generate component welcome

Folder Structure:

Dependencies:

"dependencies": {
    "@angular/animations": "^17.3.0",
    "@angular/common": "^17.3.0",
    "@angular/compiler": "^17.3.0",
    "@angular/core": "^17.3.0",
    "@angular/forms": "^17.3.0",
    "@angular/platform-browser": "^17.3.0",
    "@angular/platform-browser-dynamic": "^17.3.0",
    "@angular/platform-server": "^17.3.0",
    "@angular/router": "^17.3.0",
    "@angular/ssr": "^17.3.0",
    "express": "^4.18.2",
    "rxjs": "~7.8.0",
    "tslib": "^2.3.0",
    "zone.js": "~0.14.3"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "^17.3.0",
    "@angular/cli": "^17.3.0",
    "@angular/compiler-cli": "^17.3.0",
    "@types/express": "^4.17.17",
    "@types/jasmine": "~5.1.0",
    "@types/node": "^18.18.0",
    "jasmine-core": "~5.1.0",
    "karma": "~6.4.0",
    "karma-chrome-launcher": "~3.2.0",
    "karma-coverage": "~2.2.0",
    "karma-jasmine": "~5.1.0",
    "karma-jasmine-html-reporter": "~2.1.0",
    "typescript": "~5.4.2"
  }

Code Example:

HTML

<!-- welcome.component.html -->

<p>Welcome, {{ username }}!</p>

HTML

<!-- app.component.html -->

<app-welcome></app-welcome>

JavaScript

//welcome.component.ts

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

@Component({
    selector: 'app-welcome',
    templateUrl: './welcome.component.html',
    styleUrls: ['./welcome.component.css']
})
export class WelcomeComponent {
    username: string = 'Sourav Sharma';
}

Run the Application using the following command.

ng serve --open

Output:

Property Binding

Property binding is another one-way data binding technique in Angular that allows you to bind a property of a DOM element to a component’s property. This binding is achieved using square brackets [] in the HTML template.

Syntax of Property Binding:

<element [property]="expression"></element>

Features of Property Binding:

• Binding component properties to HTML element properties.
• Dynamic updates based on component property changes.
• Ideal for handling properties like disabled, src, href, etc.

Example of Property Binding:

Step 1: Create Angular Project

ng new property-binding-example
cd property-binding-example

Step 2: Create Component

ng generate component button

Folder Structure:

Dependencies:

"dependencies": {
    "@angular/animations": "^17.3.0",
    "@angular/common": "^17.3.0",
    "@angular/compiler": "^17.3.0",
    "@angular/core": "^17.3.0",
    "@angular/forms": "^17.3.0",
    "@angular/platform-browser": "^17.3.0",
    "@angular/platform-browser-dynamic": "^17.3.0",
    "@angular/platform-server": "^17.3.0",
    "@angular/router": "^17.3.0",
    "@angular/ssr": "^17.3.0",
    "express": "^4.18.2",
    "rxjs": "~7.8.0",
    "tslib": "^2.3.0",
    "zone.js": "~0.14.3"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "^17.3.0",
    "@angular/cli": "^17.3.0",
    "@angular/compiler-cli": "^17.3.0",
    "@types/express": "^4.17.17",
    "@types/jasmine": "~5.1.0",
    "@types/node": "^18.18.0",
    "jasmine-core": "~5.1.0",
    "karma": "~6.4.0",
    "karma-chrome-launcher": "~3.2.0",
    "karma-coverage": "~2.2.0",
    "karma-jasmine": "~5.1.0",
    "karma-jasmine-html-reporter": "~2.1.0",
    "typescript": "~5.4.2"
  }

Code Example:

HTML

<!-- app.component.html -->

<app-button></app-button>

HTML

<!-- button.component.html -->

<button [disabled]="isDisabled" 
    (click)="toggleDisabled()">Toggle</button>

JavaScript

// button.component.ts

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

@Component({
    selector: 'app-button',
    templateUrl: './button.component.html',
    styleUrls: ['./button.component.css']
})
export class ButtonComponent {
    isDisabled: boolean = true;

    toggleDisabled() {
        this.isDisabled = !this.isDisabled;
    }
}

Run the Application using the following command

ng serve --open

Output:

Difference between interpolation and property binding in Angular

In Angular, interpolation and property binding are two ways to bind data and display it in the view. Here’s a tabular comparison between interpolation and property binding:

Feature	Interpolation	Property Binding
Syntax	{{ expression }}	[property]=”expression”
Use case	One-way binding for displaying data	One-way binding for setting an element’s property
Direction of data flow	Component to view	Component to view
Binding to DOM properties	Works with element content	Works with element properties
Example	`<p>{{ message }}</p>`	`<input [value]=”username”>`
Expressions	Allows simple expressions	Allows complex expressions and method calls
Data types	Handles strings and simple variables	Handles any valid JavaScript expressions
Dynamic updates	Automatically updates when data changes	Automatically updates when data changes
Angular Directive Support	Limited to built-in directives like ngIf, ngFor, etc.	Supports all directives including custom directives

Summary:

Interpolation and property binding are powerful techniques in Angular for achieving one-way data binding. Interpolation is ideal for displaying dynamic data directly in templates, using a simple {{ }} syntax. On the other hand, property binding is more suited for binding component properties to HTML element properties, allowing for dynamic updates based on changes in the component. Understanding the differences between these two techniques will empower you to choose the right approach for different scenarios in your Angular applications.