Template expressions and statements in Angular - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a template expression in Angular?

A template expression is a piece of code written inside double curly braces {{ }} that Angular evaluates and displays in the template. It can access component properties and methods but should be simple and fast.

beginner

How do template statements differ from template expressions in Angular?

Template statements are code snippets inside event bindings like (click) that respond to user actions. They can call methods or change component state. Template expressions only display values and cannot change state.

intermediate

Can you use loops or conditionals inside Angular template expressions? Why or why not?

No, Angular template expressions are simple and do not support loops or conditionals directly. Complex logic should be handled in the component class or with Angular directives like *ngIf or *ngFor.

intermediate

What happens if a template expression throws an error during evaluation?

If a template expression throws an error, Angular catches it and usually shows a blank or fallback value in the UI. It does not crash the app but logs the error in the console for debugging.

beginner

Give an example of a template statement that updates a component property on a button click.

Example: Increase increases the 'count' property by 1 each time the button is clicked.

Which of the following is a valid Angular template expression?

A *ngIf="isVisible"

B (click)="updateName()"

C {{ userName }}

D <div>{{ for(let i=0; i<5; i++) }}</div>

Template expressions are inside {{ }} and display values like {{ userName }}. (click) and *ngIf are statements or directives, and loops are not allowed inside expressions.

What does the template statement (click)="increment()" do?

A Calls the increment() method when the element is clicked

B Displays the increment() method's return value

C Binds the increment() method to a variable

D Prevents the click event

The (click) statement listens for clicks and calls the increment() method when the user clicks the element.

Can you write a conditional (if) statement inside an Angular template expression?

A No, use *ngIf directive instead

B Yes, but only with ternary operators

C Yes, using standard JavaScript if syntax

D No, Angular does not support any conditionals

Angular template expressions do not support if statements. Use the *ngIf directive to conditionally show or hide elements.

What will happen if a template expression tries to access a property that does not exist?

A The app crashes immediately

B Angular shows nothing and logs an error in the console

C Angular shows an error message in the UI

D Angular creates the property automatically

Angular does not crash but shows no value and logs an error in the browser console for debugging.

Which Angular feature should you use to repeat a block of HTML multiple times?

A (repeat) event

B Template statement

C Template expression

D *ngFor directive

*ngFor is the Angular directive designed to repeat HTML blocks for each item in a list.

Explain the difference between template expressions and template statements in Angular.

Think about where you use {{ }} versus (event) in templates.

Describe how you would conditionally show a message in Angular templates.

Remember Angular directives control structure, not template expressions.