NG Interview Set I - API Questions

Question 1

What does this line do? @HostBinding('[class.valid]') isValid;

Answer 1

• Applies the css class ‘valid’ to whatever is using this directive conditionally based on the value of isValid

Question 2

Why would you use renderer methods instead of using native element methods?

Answer 2

• Potentially if you’re rendering to something besides the browser, e.g. rendering native elements on a mobile device, or server side rendering (?)

Question 3

What is the point of calling renderer.invokeElementMethod(rendererEl, methodName)?

Answer 3

• To invoke a method on a particular element but avoid direct DOM access (so we don’t tie our code just to the browser)

Question 4

How would you control size of an element on resize of the window in a component?

Answer 4

``

@HostListener(‘window:resize’, [‘$event’]) onResize(event: any) { this.calculateBodyHeight(); }

Question 5

What would be a good use for NgZone service?

Answer 5

• Running an asynchronous process outside of Angular change detection

Question 6

How would you protect a component being activated through the router?

Answer 6

• Route Guards

Question 7

How would you insert an embedded view from a prepared TemplateRef?

Answer 7

` viewContainerRef.

createEmbeddedView(templateRef);`