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Mastering Filtering and Data Types in Angular 2

Angular 2 is a popular framework for building web applications, and it has several features that make it an excellent choice for developers. Two of these features are filtering and data types and structure.

In this article, we will explore these features in detail and provide you with the information you need to improve your understanding of Angular 2.

Filtering in Angular 2

Filtering in Angular 2 can be done in two ways. The first method is by using the filter() method.

This method is available in JavaScript and can be used to filter an array of data. To filter an array, we can use the filter() method like this:

“`typescript

data.filter(function(item) {

return item.name === ‘xyz’;

});

“`

This code will return an array of items whose name is ‘xyz’.

The second method for filtering data in Angular 2 is by using pipes. A pipe is a feature in Angular 2 that allows you to modify data by using a filter.

To create a pipe, we can use the pipe() method like this:

“`typescript

import { Pipe, PipeTransform } from ‘@angular/core’;

@Pipe({

name: ‘filterByName’

})

export class FilterByNamePipe implements PipeTransform {

transform(data: any[], filter: string): any[] {

if (!data || !filter) {

return data;

}

return data.filter(item =>

item.name.toLocaleLowerCase().indexOf(filter.toLocaleLowerCase()) !== -1);

}

}

“`

In this example, we are defining a pipe called ‘filterByName’ that accepts two arguments: data and filter. The code uses the filter() method to filter the data by the input filter string.

Using ngOnInit() as a lifecycle hook is an effective way to filter an array in Angular 2. The ngOnInit() method is called only once, after the component is initialized.

We can use this method to initialize data and perform any necessary filtering.

Data Types and Structure in Angular 2

Angular 2 has an Array type that allows us to create and manipulate arrays of data. The Array type is a built-in JavaScript type and provides numerous methods for manipulating data within the array.

Angular 2’s MVW (Model-View-Whatever) architecture is a powerful feature that allows developers to create organized and structured web applications. This architecture separates the presentation and logic layers from the data model, making it easier to manage and maintain code.

When it comes to data types and structures, there are some differences between Angular 2 and Angular 1. Angular 2 provides a more concise syntax for defining data structures, and it has a more modular design than Angular 1.

It also offers a cleaner separation of concerns and provides more flexibility for customizing data structures.

Conclusion

In this article, we explored filtering and data types and structures in Angular 2. We learned how to use the filter() method and pipes to filter an array, and we also discussed the differences between Angular 2 and Angular 1 regarding data types and structures.

With this information in hand, you can confidently start building Angular 2 web applications that are efficient, structured, and maintainable.

Creating a new Pipe in Angular 2

In Angular 2, pipes are a powerful feature that can be used for filtering data. Creating a new pipe in Angular 2 is a straightforward process that involves creating a new class, implementing the PipeTransform interface, and using the @Pipe decorator to register the pipe.

Here is an example of how to create a new pipe in Angular 2:

1. Create a new file called my-pipe.ts in your app’s src/app folder.

2. In my-pipe.ts, import the Pipe and PipeTransform classes from the @angular/core module:

“`typescript

import { Pipe, PipeTransform } from ‘@angular/core’;

“`

3.

Define your pipe class and implement the PipeTransform interface:

“`typescript

@Pipe({ name: ‘myPipe’ })

export class MyPipe implements PipeTransform {

transform(value: string, arg1: string, arg2: number): string {

// Your code here

}

}

“`

4. In the constructor of your pipe class, you can inject any services or dependencies you need:

“`typescript

constructor(private myService: MyService) { }

“`

5.

Implement the transform method, which takes the input value and any arguments you need to pass to your pipe. This method should return the output value of your pipe:

“`typescript

transform(value: string, arg1: string, arg2: number): string {

const transformedValue = /* Your transformation logic here */

return transformedValue;

}

“`

6.

Use the @Pipe decorator to register your pipe:

“`typescript

@Pipe({ name: ‘myPipe’ })

“`

7. Import your pipe in your app module:

“`typescript

import { MyPipe } from ‘./my-pipe’;

“`

8.

Declare your pipe in the declarations list of your app module:

“`typescript

@NgModule({

declarations: [MyPipe],

// more code here

})

“`

Using ngFor directive

The ngFor directive in Angular 2 is a powerful built-in directive that can be used to render a list of data. It is a simple way to loop over an array of data and create a template for each item in the array.

To use the ngFor directive, simply add the directive to an HTML element and provide it with an array of data to loop over:

“`html

  • {{ item }}

“`

In this example, the ngFor directive is added to a list element. The items property in the component class is an array of data that is looped over, and the data is rendered in an li element.

Implementing live search filter using ngFor and ngOnInit()

In this example implementation, we will show how to implement a live search filter using the ngFor directive and ngOnInit() method in Angular 2. 1.

Start by creating a new component using the CLI:

“`bash

ng g c my-component

“`

2. In the my-component.component.ts file, define the component class and create an array of data to filter:

“`typescript

import { Component } from ‘@angular/core’;

@Component({

selector: ‘app-my-component’,

templateUrl: ‘./my-component.component.html’,

styleUrls: [‘./my-component.component.css’]

})

export class MyComponentComponent {

items = [‘Apple’, ‘Banana’, ‘Cherry’, ‘Date’];

filteredItems = [];

ngOnInit() {

this.filteredItems = this.items;

}

onSearch(event: any) {

const searchText = event.target.value;

this.filteredItems = this.items.filter(item =>

item.toLowerCase().includes(searchText.toLowerCase())

);

}

}

“`

In this example, we are creating an array of items and storing it in the items property.

We are also defining a filteredItems property, which we will use to store the filtered version of the items array. In the ngOnInit() method, we initialize the filteredItems array to be the same as the items array.

When the user types in the search box, we use the onSearch() method to update the filteredItems array by filtering the items array based on the search text. The result of the filtering is then assigned to the filteredItems property.

3. In the my-component.component.html file, add an input element for the search box and use the ngFor directive to render the filtered items:

“`html

  • {{ item }}

“`

In this example, we are adding an input element for the search box and binding the (keyup) event to the onSearch() method in the component class.

We are also using the ngFor directive to loop over the filteredItems array and render each item as an li element.

Conclusion

In this extension, we discussed how to create a new pipe in Angular 2, how to use the ngFor directive to render a list of data, and how to implement a live search filter using the ngFor and ngOnInit() methods. By understanding these concepts, developers can create powerful and efficient web applications using Angular 2.

In conclusion, this article covered the key concepts of filtering and data types and structures in Angular 2. We learned how to filter data using pipes in Angular 2, create a new pipe in Angular 2, use the ngFor directive to render a list of data, and implement a live search filter using ngFor and ngOnInit().

These features help developers build more efficient, structured, and maintainable web applications. By mastering these Angular 2 concepts, developers can enhance their skills and create robust web applications that meet the requirements of modern-day business.

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