Day 2 Components and Promises

Day 2 - Components and Promises


notepad	Componentization of notepad
pop-quiz-ex1	Solution of class exercise
fun-with-promises	Introduction to promises in JS

We agreed that writing full scale applications in one component is difficult to maintain, which is why angular was built to support multi-component applications
We created a title-presneter component that presents a title
We have used the @Input Decorator to add input properties that may be passed through the HTML
We saw the difference between passing data using [prop]="expression" syntax and prop="text" syntax. Where the first is used to bind data from the view model, and the second is used to pass a hard coded string.
We used the cli to auto-generate components using ng g c components/component-name. See more details Here
We used the @Output Directive and the EventMitter<T> class to create our own events and raise them in our components
We used the (event)="action()" Syntax to respond to an event in the container component
We used the $event keyword to access event data

Attached is a presentation and a video that present an exercise and its solution
The presentation
The Video

We defined a promise as an object that tells us if an action that takes time has completed, and what is the result
We saw that we can not "pull" that information, but rather have to use the .then and .catch methods and provide callbacks that will be called when the promise completes
We saw how to create a promise using the Promise Constructor.
We understood what async and await keywords do and how do they affect the compilation
We understood that the .then method, and the async keywords, also create promises, out of other promises
We saw how to ue Promise.resolve to create a promise that is already completed when it is created
We saw how to use Promise.all and Promise.race to group promises together and wrap them in a single promise that returns all the results from all the promises or from the first one to complete.