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Button Clicks - Introduction to Angular 2 with JavaScript - Part 3

This is the third in a series about building a simple AngularJS application. If you haven't already, check out part 1 and part 2.


In part 1 we built a simple component that displayed a template to the screen. In part 2 we showed how to bind a Class variable to an input and a display. Let's review the Angular component code:

(function(app) {
app.AppComponent =
selector: 'my-app',
template: '<h1>Hello {{helloTo}}</h1>' +
'<input type="text" [value]="helloTo" (input)="helloTo=$" /><br/>' +
'<input type="text" [(ngModel)]="helloTo" /><br/>'
constructor: function() {
this.helloTo = "World"
})( || ( = {}));

The component is wrapped in an IIFE function; and the Angular application is stored in the variable. The component is given a selector, my-app, which is in essence the name. The template includes two inputs demonstrating two different ways to bind to values in Angular 2.

The Class contains a single variable, helloTo, which is used as the source for binding.

Change the Template

Another common element required when developing applications is to run code when a button is clicked. In Angular 1 we used the ngClick event. Angular 2 uses a similar concept, but is slightly different implementation syntax. Here is the component's template as a reminder:

template: '<h1>Hello {{helloTo}}</h1>' +
'<input type="text" [value]="helloTo"
(input)="helloTo=$" />
<br/>' +
'<input type="text" [(ngModel)]="helloTo" /><br/>'

The template consists of a header which binds to the helloTo variable. It has two inputs, both representing different methods to change the helloTo variable.

We'll add one more item to the template. Here is a button:

'<button (click)="onReset()">reset</button><br/>' +

I put the button after the header, but before the inputs. Instead of using an ngClick directive, the directive is named click, and is enclosed by parenthesis. The click statement on the button will call a method inside the component's class.

Create the Click Handler

We want to the button to reset the helloTo variable to its default value, World. After the helloTo variable is created in the Class, add a function named onReset():

this.onReset = function(){
this.helloTo = "World";

Run the code, and you should see something like this:

Change one of the inputs, and click the reset button. The app should go back to its default state.

Play with the code here

Final Thoughts

I enjoyed my experiments with Angular 2 and JavaScript. Based on available documentation, I'd be cautious about jumping into Angular 2 deep at the time of this writing. If I were going to; I'd focus on TypeScript. The full documentation for JavaScript is not there yet and most of the community questions revolve around TypeScript answers, which are not always easily portable to JavaScript. Despite all this; I'm cautiously optimistic about our Angular 2 future.

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