Angular 2 Data Binding - Angular 2

What is Data binding in Angular 2?

Description

Data binding performs synchronization of data between the model and view components. For displaying the component property, user can enter the name in view template, by enclosing in double curly braces. Two-way data binding combines property and event binding in a single notation using directive ngModel.

Example

Below example describes the use of data binding in Angular 2:

Above code includes below configuration options

  • User can configure index.html file using typescript version. SystemJS transpilers TypeScript to JavaScript before running the application using the transpiler option.
  • If the user does not want to transpile to JavaScript before running the application, they can see the compiler warnings and errors hidden in the browser.
  • The TypeScript generates metadata for each and every class of the code when the emitDecoratorMetadata option is set. If you don't specify this option, large amount of unused metadata will be generated which affects the file size and impact on the application runtime.
  • Angular 2 includes packages form the app folder where files will have the .ts extension.
  • Next it loads the main component file from the app folder. If main component file is not found, then it will display the error in the console.
  • When Angular calls the bootstrap function in main.ts, it reads the Component metadata, finds the 'app' selector, locates an element tag named app, and loads the application between those tags.

To run the code, TypeScript(.ts) files are needed which should be saved under the app folder.

data_binding_main.ts

Now create a component in TypeScript(.ts) file as shown below:

data_binding_app.component.ts

  • @Component is a decorator which uses configuration object for creating the component and its view.
  • Selector creates an instance of the component where it finds <my-app> tag in parent HTML.
  • Next is *ngFor directive which creates view exports which are binded in the template. * is shorthand for using Angular 2 template syntax with the template tag.
  • Local variable Item can be referenced in the template to get the index of an array. By clicking on the item value, onItemClicked() event will get activated and Angular 2 will bind the model name from the array with the local variable template.
  • By clicking on item name from the list, model name clickedItem will be binded with name and it displays the item name in the text box.

Output

Below steps can be carried out to see how above code works:

  • Save above HTML code as index.html file as and use the above app folder which contains .ts files.
  • Open the terminal window and enter below command:

  • After few minutes, a browser tab should open and should display the output as shown below.

OR this file can be run in another way:

  • Save above HTML code as angular2_hello_world.html file in the server root folder.
  • Open this HTML file as http://localhost/angular2_hello_world.html and output as shown below will be displayed.

Example displays the item name in the text box by clicking on item name from the list.

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