angular filter array of objects with code examples

Angular is a popular JavaScript framework for building web applications. It provides a set of tools for working with arrays of objects, including filters. Filters in Angular are used to transform data before it is displayed to the user. They can be used to sort, format, or search data. In this article, we will discuss how to filter an array of objects in Angular and provide code examples to illustrate the different ways to do it.

Before diving into the code, let's take a look at what an array of objects is and how it can be used in Angular. An array of objects is a collection of objects where each object represents a data item. For example, you may have an array of books, each book object may have properties such as title, author, and publication date. In Angular, you can use an array of objects to store data for a component, and then use filters to transform the data for display to the user.

Now, let's take a look at how to filter an array of objects in Angular. There are several ways to do this, including using pipes, using custom functions, and using the JavaScript Array.filter() method.

Using Pipes

Pipes are a simple way to filter an array of objects in Angular. Pipes are used to transform data in a template before it is displayed to the user. In Angular, there are several built-in pipes that you can use to filter arrays, including the filter and orderBy pipes.

Here's an example of how to use the filter pipe to filter an array of books based on the author's name:

<div *ngFor="let book of books | filter: { author: 'John Doe' }">
  {{ book.title }}
</div>

In this example, the filter pipe is used to filter the books array based on the author's name. The filter pipe takes an object as an argument, with the properties to be used for filtering. In this case, we are filtering by the author's name, which is set to 'John Doe'.

Using Custom Functions

Another way to filter an array of objects in Angular is to create a custom function. Custom functions allow you to have more control over the filtering process and can be used in a variety of ways.

Here's an example of a custom function that filters an array of books based on the author's name:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  template: `
    <div *ngFor="let book of filteredBooks">
      {{ book.title }}
    </div>
  `
})
export class AppComponent {
  books = [
    { title: 'Book 1', author: 'John Doe' },
    { title: 'Book 2', author: 'Jane Doe' },
    { title: 'Book 3', author: 'John Doe' },
  ];

  filteredBooks = [];

  ngOnInit() {
    this.filteredBooks = this.books.filter(book => book.author === 'John Doe');
  }
}

In this example, the custom function is defined in the ngOnInit() method. The function uses the Array.filter() method to filter the books array based on the author's name. The filtered books are then stored in the filteredBooks array, which is used in the template to display the filtered data.

Using the Array.filter() Method

The Array.filter() method is a built-in JavaScript function that can be used to filter an array of objects. It is a convenient and flexible way to filter an array and can be used in Angular as well.

Here's an example of using the Array.filter() method to filter an array of books based on the author's name:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  template: `
    <div *ngFor="let book of filteredBooks">
      {{ book.title }}
    </div>
  `
})
export class AppComponent {
  books = [
    { title: 'Book 1', author: 'John Doe' },
    { title: 'Book 2', author: 'Jane Doe' },
    { title: 'Book 3', author: 'John Doe' },
  ];

  filteredBooks = [];

  ngOnInit() {
    this.filteredBooks = this.books.filter(book => book.author === 'John Doe');
  }
}

In this example, the Array.filter() method is used to filter the books array based on the author's name. The filtered books are then stored in the filteredBooks array, which is used in the template to display the filtered data.

Sorting an Array of Objects

Sorting an array of objects in Angular is another common task. There are several ways to sort an array of objects, including using pipes and custom functions.

Here's an example of how to sort an array of books by title using the orderBy pipe:

<div *ngFor="let book of books | orderBy: 'title'">
  {{ book.title }}
</div>

In this example, the orderBy pipe is used to sort the books array by the title property. The orderBy pipe takes a single argument, which is the property to sort by. In this case, we are sorting by the title property, which is set to 'title'.

Here's an example of how to sort an array of books by publication date using a custom function:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  template: `
    <div *ngFor="let book of sortedBooks">
      {{ book.title }}
    </div>
  `
})
export class AppComponent {
  books = [
    { title: 'Book 1', author: 'John Doe', publicationDate: '2020-01-01' },
    { title: 'Book 2', author: 'Jane Doe', publicationDate: '2021-01-01' },
    { title: 'Book 3', author: 'John Doe', publicationDate: '2019-01-01' },
  ];

  sortedBooks = [];

  ngOnInit() {
    this.sortedBooks = this.books.sort((a, b) => {
      return new Date(a.publicationDate) - new Date(b.publicationDate);
    });
  }
}

In this example, the custom function is defined in the ngOnInit() method. The function uses the Array.sort() method to sort the books array by

Popular questions

Here are five questions and answers related to filtering arrays of objects in Angular with code examples:

1. What is the Array.filter() method in JavaScript, and how is it used in Angular?

   • The Array.filter() method is a built-in JavaScript function that can be used to filter an array of objects based on a given condition. In Angular, the Array.filter() method can be used to filter an array of objects in a component and display the filtered data in the template.

2. How can we filter an array of objects in Angular based on a specific property value?

   • To filter an array of objects in Angular based on a specific property value, we can use the Array.filter() method. For example, to filter an array of books based on the author's name, we can write the following code:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  template: `
    <div *ngFor="let book of filteredBooks">
      {{ book.title }}
    </div>
  `
})
export class AppComponent {
  books = [
    { title: 'Book 1', author: 'John Doe' },
    { title: 'Book 2', author: 'Jane Doe' },
    { title: 'Book 3', author: 'John Doe' },
  ];

  filteredBooks = [];

  ngOnInit() {
    this.filteredBooks = this.books.filter(book => book.author === 'John Doe');
  }
}

3. Can we sort an array of objects in Angular, and if so, how?
   • Yes, we can sort an array of objects in Angular. There are several ways to sort an array of objects in Angular, including using pipes and custom functions. For example, to sort an array of books by title, we can use the orderBy pipe as follows:

<div *ngFor="let book of books | orderBy: 'title'">
  {{ book.title }}
</div>

4. Can we filter and sort an array of objects in Angular at the same time?
   • Yes, we can filter and sort an array of objects in Angular at the same time. To do so, we can use the Array.filter() method to filter the array and then sort the filtered array using a pipe or custom function. For example, to filter and sort an array of books by author and publication date, we can write the following code:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  template: `
    <div *ngFor="let book of sortedBooks">
      {{ book.title }}
    </div>
  `
})
export class AppComponent {
  books = [
    { title: 'Book 1', author: 'John Doe', publicationDate: '2020-01-01' },
    { title: 'Book 2', author: 'Jane Doe', publicationDate: '2021-01-01' },
    { title: 'Book 3', author: 'John Doe', publicationDate: '2019-01-01' },
  ];

  sortedBooks = [];

  ngOnInit() {
    this.sortedBooks = this.books
      .filter(book => book.author === 'John Doe')
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