Angular Directives

What is the purpose of the ngIf directive in Angular?

• To conditionally show or hide elements in the DOM

• To handle form submissions

• To loop through an array of items

• To define a new component

How do you use the ngIf directive in an Angular template?

• Example:

  Content to show when condition is true

• Wrap the entire template in ngIf

• Example:

• Use ngIf in the TypeScript file

Explain the difference between ngIf and ngFor directives in Angular.

• ngIf is used for creating new elements, while ngFor is used for updating existing elements

• ngIf is used for looping over arrays, while ngFor is used for conditional rendering

• The main difference between ngIf and ngFor directives in Angular is that ngIf is used for conditionally rendering elements, while ngFor is used for iterating over a collection.

• ngIf is used for styling elements, while ngFor is used for data binding

When would you use the ngIf directive over ngFor in Angular?

• When you want to conditionally show or hide a single element based on a boolean expression.

• When you want to conditionally show or hide multiple elements based on a boolean expression.

• When you want to loop over a collection of items and display them dynamically.

• When you want to apply a specific style to a group of elements based on a condition.

What does the ngFor directive do in Angular?

• Creates a new Angular component

• Applies styling to HTML elements

• Defines routing paths in Angular

• Iterates over a collection of data and renders each item in the collection as a separate instance of a template.

Provide an example of using ngFor in an Angular template.

• items = ['item1', 'item2', 'item3'];

  {{ items.item }}

• items = ['item1', 'item2', 'item3'];

  {{ item }}

• items = ['item1', 'item2', 'item3'];

  {{ item }}

• items = ['item1', 'item2', 'item3'];

  {{ items }}

How can you track the index of ngFor loop in Angular?

• index = i

• let i = index

• ngFor.index

• let j = index

What is the syntax for using ngFor with an index in Angular?

• *ngFor='let item of items; let i = index'

• *ngFor='let item of items; let i = i'

• *ngFor="let item of items; let i = index"

• *ngFor='let item of items; index as i'

Explain the trackBy function in ngFor directive.

• The trackBy function in ngFor directive is used to filter out specific items from the list

• The trackBy function in ngFor directive is used to provide a unique identifier for each item in the list to improve performance.

• The trackBy function in ngFor directive is used to apply styling to each item in the list

• The trackBy function in ngFor directive is used to change the order of items in the list

Why is it important to use trackBy function with ngFor in Angular?

• It is important to use trackBy function with ngFor in Angular to slow down rendering performance

• It is important to use trackBy function with ngFor in Angular to optimize rendering performance and prevent unnecessary re-rendering of elements.

• It is important to use trackBy function with ngFor in Angular to cause errors in the application

• It is important to use trackBy function with ngFor in Angular to add unnecessary complexity to the code