Gain insights into Angular’s built-in directives and pipes, and delve into creating custom ones. Learn about their real-world applications to boost your project's performance and code readability.

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Directives and pipes are incredible and often undervalued features of the Angular framework. They allow us to write efficient code, improve application performance, and omit code duplications.

In this course, you will learn about the theory and the working mechanisms of built-in directives and pipes in Angular. You’ll also implement some custom directives and pipes to learn about their real-world application cases. With this course, you will improve your Angular skills and refine your project’s codebase to increase the performance and readability of your code.

Directives and Pipes in Angular

# Solution

Here’s one possible implementation of what the solution for this task may look like:


# This file is used by the build system to adjust CSS and JS output to support the specified browsers below.
# For additional information regarding the format and rule options, please see:
# https://github.com/browserslist/browserslist#queries

# For the full list of supported browsers by the Angular framework, please see:
# https://angular.io/guide/browser-support

# You can see what browsers were selected by your queries by running:
#   npx browserslist

last 1 Chrome version
last 1 Firefox version
last 2 Edge major versions
last 2 Safari major versions
last 2 iOS major versions
Firefox ESR
not IE 11 # Angular supports IE 11 only as an opt-in. To opt-in, remove the 'not' prefix on this line.


# Editor configuration, see https://editorconfig.org
root = true

[*]
charset = utf-8
indent_style = space
indent_size = 2
insert_final_newline = true
trim_trailing_whitespace = true

[*.ts]
quote_type = single

[*.md]
max_line_length = off
trim_trailing_whitespace = false


# See http://help.github.com/ignore-files/ for more about ignoring files.

# compiled output
/dist
/tmp
/out-tsc
# Only exists if Bazel was run
/bazel-out

# dependencies
/node_modules

# profiling files
chrome-profiler-events*.json

# IDEs and editors
/.idea
.project
.classpath
.c9/
*.launch
.settings/
*.sublime-workspace

# IDE - VSCode
.vscode/*
!.vscode/settings.json
!.vscode/tasks.json
!.vscode/launch.json
!.vscode/extensions.json
.history/*

# misc
/.sass-cache
/connect.lock
/coverage
/libpeerconnection.log
npm-debug.log
yarn-error.log
testem.log
/typings

# System Files
.DS_Store
Thumbs.db


# DirectivesAndPipesCourse

This project was generated with [Angular CLI](https://github.com/angular/angular-cli) version 12.1.2.

## Development server

Run `ng serve` for a dev server. Navigate to `http://localhost:4200/`. The app will automatically reload if you change any of the source files.

## Code scaffolding

Run `ng generate component component-name` to generate a new component. You can also use `ng generate directive|pipe|service|class|guard|interface|enum|module`.

## Build

Run `ng build` to build the project. The build artifacts will be stored in the `dist/` directory.

## Running unit tests

Run `ng test` to execute the unit tests via [Karma](https://karma-runner.github.io).

## Running end-to-end tests

Run `ng e2e` to execute the end-to-end tests via a platform of your choice. To use this command, you need to first add a package that implements end-to-end testing capabilities.

## Further help

To get more help on the Angular CLI use `ng help` or go check out the [Angular CLI Overview and Command Reference](https://angular.io/cli) page.


// Karma configuration file, see link for more information
// https://karma-runner.github.io/1.0/config/configuration-file.html

module.exports = function (config) {
  config.set({
    basePath: '',
    frameworks: ['jasmine', '@angular-devkit/build-angular'],
    plugins: [
      require('karma-jasmine'),
      require('karma-chrome-launcher'),
      require('karma-jasmine-html-reporter'),
      require('karma-coverage'),
      require('@angular-devkit/build-angular/plugins/karma')
    ],
    client: {
      jasmine: {
        // you can add configuration options for Jasmine here
        // the possible options are listed at https://jasmine.github.io/api/edge/Configuration.html
        // for example, you can disable the random execution with `random: false`
        // or set a specific seed with `seed: 4321`
      },
      clearContext: false // leave Jasmine Spec Runner output visible in browser
    },
    jasmineHtmlReporter: {
      suppressAll: true // removes the duplicated traces
    },
    coverageReporter: {
      dir: require('path').join(__dirname, './coverage/directives-and-pipes-course'),
      subdir: '.',
      reporters: [
        { type: 'html' },
        { type: 'text-summary' }
      ]
    },
    reporters: ['progress', 'kjhtml'],
    port: 9876,
    colors: true,
    logLevel: config.LOG_INFO,
    autoWatch: true,
    browsers: ['Chrome'],
    singleRun: false,
    restartOnFileChange: true
  });
};


/* To learn more about this file see: https://angular.io/config/tsconfig. */
{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "outDir": "./out-tsc/app",
    "types": []
  },
  "files": [
    "src/main.ts",
    "src/polyfills.ts"
  ],
  "include": [
    "src/**/*.d.ts"
  ]
}


/* To learn more about this file see: https://angular.io/config/tsconfig. */
{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    "outDir": "./dist/out-tsc",
    "forceConsistentCasingInFileNames": true,
    "strict": true,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true,
    "sourceMap": true,
    "declaration": false,
    "downlevelIteration": true,
    "experimentalDecorators": true,
    "moduleResolution": "node",
    "importHelpers": true,
    "target": "es2017",
    "module": "es2020",
    "lib": [
      "es2018",
      "dom"
    ]
  },
  "angularCompilerOptions": {
    "enableI18nLegacyMessageIdFormat": false,
    "strictInjectionParameters": true,
    "strictInputAccessModifiers": true,
    "strictTemplates": true
  }
}


/* To learn more about this file see: https://angular.io/config/tsconfig. */
{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "outDir": "./out-tsc/spec",
    "types": [
      "jasmine"
    ]
  },
  "files": [
    "src/test.ts",
    "src/polyfills.ts"
  ],
  "include": [
    "src/**/*.spec.ts",
    "src/**/*.d.ts"
  ]
}


React

Dart

GoJS React

Typescript React

Vue.js

# Explanation
Key points to consider while implementing this exercise are:

- How to react and change the style on mouse events.

- How to emit events from the directive.

Reacting on mouse events are solved using `HostListener`, like so:

```tsx
@HostListener('mouseenter')
onMouseEnter() {
    this.elementRef.nativeElement.style.transform = 'scale(1.1)';
}
```

Now, we need a way of informing listeners about our actions. For this, we need to use the `Output` property, like this:

```tsx
@Output() zoom = new EventEmitter<boolean>();
```

We can emit values when changes occur, as shown below:


```tsx
@HostListener('mouseenter')
onMouseEnter() {
    this.zoom.emit(true);
}

@HostListener('mouseleave')
onMouseLeave() {
    this.zoom.emit(false);
}
```

**_That’s all there is to it!
!_**

Let’s confirm the task result with the expected result and explanation.


Solution: Handle Events with a Custom Attribute Directive

Let’s confirm the task result with the expected result and explanation.

Getting Started

Directives

Test: Built-in Directives

Attribute Directives

Test: Attribute Directives

Structural Directives

Test: Structural Directives

Create Your First Data Pipeline with a Dashboard

Advanced Techniques Using Directives

Test: Advanced Directives

Directives Summary

Pipes

Test: Pipes

Pipes summary

Build an E-book Reader in Angular With Gutendex API

Solution: Handle Events with a Custom Attribute Directive

Solution