What is Data Binding in Angular?
💡 Concept Name
Data Binding – A mechanism in Angular that connects the component logic to the UI and enables dynamic interaction.
📘 Quick Intro
Data binding in Angular is the process of synchronizing data between the component class and its corresponding template (view). It allows automatic updates to the view when the model changes and vice versa.
🧠 Analogy / Short Story
Think of data binding like a live translator between your brain (component) and your speech (UI). When your thoughts (data) change, your speech updates instantly—no manual syncing required!
🔧 Technical Explanation
- 🔁 Angular provides different types of data binding: Interpolation, Property Binding, Event Binding, and Two-Way Binding.
- 📤 One-way binding sends data from component to view or vice versa.
- 🔄 Two-way binding synchronizes data in both directions using
[(ngModel)]. - ⚡ Enables interactive and dynamic UI updates.
🎯 Purpose & Use Case
- ✅ Display dynamic values in templates.
- ✅ Update component properties on user input.
- ✅ Sync form data and perform validation in real-time.
- ✅ Handle DOM events like click, input, change, etc.
💻 Real Code Example
// app.component.ts
export class AppComponent {
message = 'Hello World';
updateMessage() {
this.message = 'Angular is awesome!';
}
}<!-- app.component.html -->
<h2>{{ message }}</h2>
<button (click)="updateMessage()">Change Message</button>
<input [(ngModel)]="message" />Key Highlight: Demonstrates interpolation, event binding, and two-way binding all in one place.
❓ Interview Q&A
Q1: What is data binding in Angular?
A: It’s the synchronization of data between the component class and the DOM.
Q2: What are the types of data binding in Angular?
A: Interpolation, Property Binding, Event Binding, and Two-Way Binding.
Q3: What does [(ngModel)] do?
A: It enables two-way data binding between input fields and component properties.
Q4: Is two-way binding required for all fields?
A: No, it’s useful when you need real-time updates both ways.
Q5: Which module must be imported to use ngModel?
A: FormsModule from @angular/forms.
Q6: What is interpolation in Angular?
A: Using {{ }} to bind component data into HTML.
Q7: What is the difference between property and event binding?
A: Property binding sets element properties, while event binding listens to DOM events.
Q8: Can you bind styles or classes dynamically?
A: Yes, using [ngStyle] and [ngClass] directives.
Q9: Is data binding unidirectional or bidirectional by default?
A: It’s unidirectional by default; two-way requires [(ngModel)].
Q10: Why is data binding important?
A: It keeps your UI in sync with your application logic automatically.
📝 MCQs
Q1. Which directive enables two-way data binding in Angular?
- ngBind
- ngData
- ngModel
- ngControl
Q2. What symbol is used for interpolation?
- {{}}
- []
- ()
- <>
Q3. What does property binding use syntactically?
- ( )
- [ ]
- { }
- <>
Q4. Which Angular module is required to use ngModel?
- HttpClientModule
- RouterModule
- FormsModule
- BrowserModule
Q5. Which binding is used to handle events like click?
- Property binding
- Event binding
- Two-way binding
- Style binding
Q6. Can interpolation bind methods?
- Yes
- No
- Only in directives
- Only in pipes
Q7. What kind of binding does input tag with [(ngModel)] represent?
- Event
- One-way
- Two-way
- No binding
Q8. Which directive binds to style dynamically?
- ngClass
- ngBindStyle
- ngStyle
- styleBind
Q9. What happens when component data changes in one-way binding?
- Nothing
- The view updates
- The component is destroyed
- The app reloads
Q10. Is event binding part of one-way or two-way binding?
- One-way
- Two-way
- No binding
- Both
💡 Bonus Insight
Use ngModelChange if you want more control over two-way binding logic. Also, prefer reactive forms for complex form scenarios where validation and state management need to be explicit.
📄 PDF Download
Need a handy summary for your notes? Download this topic as a PDF!