Difference Between Structural and Attribute Directives

๐Ÿ’ก Concept Name

Structural vs Attribute Directives โ€“ Two primary types of Angular directives that change the layout or appearance of elements.

๐Ÿ“˜ Quick Intro

Angular provides directives to modify the DOM. Structural directives change the structure of the DOM (add/remove elements), while attribute directives change the appearance or behavior of existing elements.

๐Ÿง  Analogy / Short Story

Imagine building a Lego house: structural directives are like deciding which bricks to use or remove (affecting structure), while attribute directives are like painting or decorating the house (changing appearance without affecting structure).

๐Ÿ”ง Technical Explanation

  • ๐Ÿ—๏ธ Structural Directives: Modify the DOM layout by adding or removing elements. Examples: *ngIf, *ngFor, *ngSwitch.
  • ๐ŸŽจ Attribute Directives: Change the appearance or behavior of an element. Examples: ngClass, ngStyle, custom directives like appHighlight.
  • โš ๏ธ Structural directives are prefixed with *, while attribute directives are not.

๐ŸŽฏ Purpose & Use Case

  • โœ… Use structural directives for conditional rendering, loops, or switching views.
  • โœ… Use attribute directives to apply styles, CSS classes, or behaviors dynamically.

๐Ÿ’ป Real Code Example

<!-- Structural Directive -->
<div *ngIf="isLoggedIn">Welcome, user!</div>

<!-- Attribute Directive -->
<div [ngStyle]="{color: 'blue'}">This text is blue.</div>

Key Highlight: *ngIf adds/removes the element; ngStyle applies a style without changing structure.

โ“ Interview Q&A

Q1: What is a structural directive?
A: It changes the DOM structure by adding or removing elements.

Q2: What is an attribute directive?
A: It changes the appearance or behavior of an element without altering the DOM structure.

Q3: Name three structural directives in Angular.
A: *ngIf, *ngFor, *ngSwitch.

Q4: Name some attribute directives in Angular.
A: ngClass, ngStyle, custom directives like appHighlight.

Q5: Why is there an asterisk (*) before structural directives?
A: It tells Angular to transform the HTML using TemplateRef behind the scenes.

๐Ÿ“ MCQs

Q1. Which directive modifies the structure of the DOM?

  • [ngClass]
  • *ngIf
  • (click)
  • [ngStyle]

Q2. Which directive changes only the appearance or behavior?

  • *ngFor
  • [ngStyle]
  • *ngIf
  • *ngSwitch

Q3. What does the asterisk (*) signify in a directive like *ngIf?

  • Attribute directive
  • Style binding
  • Structural directive
  • Event binding

Q4. Which directive is used to add CSS classes dynamically?

  • *ngIf
  • [ngClass]
  • [style]
  • *ngSwitch

Q5. Can attribute directives remove DOM elements?

  • Yes
  • No
  • Sometimes
  • Only with * prefix

๐Ÿ’ก Bonus Insight

You can create your own custom structural or attribute directives in Angular using the @Directive decorator and by injecting ElementRef and Renderer2 for manipulation.

๐Ÿ“„ PDF Download

Need a handy summary for your notes? Download this topic as a PDF!

โžก๏ธ Next:

๐Ÿ’ฌ Feedback
๐Ÿš€ Start Learning
Share:

Tags: