ngx-highlightjs

Angular Highlight.js

Instant code highlighting, auto-detect language, super easy to use

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Table of Contents

• Live Demo | Stackblitz
• Installation
• Usage
• Development
• Issues
• Author
• More plugins

Installation

Install with NPM

npm i ngx-highlightjs

Usage

Import HighlightModule in your app

import { HighlightModule } from 'ngx-highlightjs';

@NgModule({
  imports: [
    HighlightModule
  ]
})
export class AppModule { }

Note: By default this will lazy-load highlight.js bundle library including all languages.

To avoid import everything from highlight.js library, you should import each language you want to highlight manually.

Import highlighting languages

To do so, use the injection token HIGHLIGHT_OPTIONS to provide options:

import { HighlightModule, HIGHLIGHT_OPTIONS } from 'ngx-highlightjs';

/**
 * Import specific languages to avoid importing everything
 * The following will lazy load highlight.js core script (~9.6KB) + the selected languages bundle (each lang. ~1kb)
 */
export function getHighlightLanguages() {
  return {
    typescript: () => import('highlight.js/lib/languages/typescript'),
    css: () => import('highlight.js/lib/languages/css'),
    xml: () => import('highlight.js/lib/languages/xml')
  };
}
 
@NgModule({
  imports: [
    HighlightModule
  ],
  providers: [
    {
      provide: HIGHLIGHT_OPTIONS,
      useValue: {
        languages: getHighlightLanguages()
      }
    }
  ],
})
export class AppModule {
}

• languages: The set of languages to register.
• lineNumber: Lazy-load lines numbers library which adds line numbers to the highlighted code element.
• config: Set highlight.js config, see configure-options.

Import highlighting theme

Import highlight.js theme from the node_modules directory in angular.json

"styles": [
  "styles.css",
  "../node_modules/highlight.js/styles/github.css",
]

Or import it in src/style.scss

@import '~highlight.js/styles/github.css';

List of all available themes from highlight.js

Use highlight directive

The following line will highlight the given code and append it to the host element

<pre><code [highlight]="code"></code></pre>

Demo stackblitz

Options

• [highlight]: (string), Accept code string to highlight, default null

• [languages]: (string[]), An array of language names and aliases restricting auto detection to only these languages, default: null

• [lineNumbers]: (boolean), A flag that indicates adding line numbers to highlighted code element

• (highlighted): Stream that emits HighlightResult object when element is highlighted.

Plus package

In version >= 4, a new sub-package were added with the following features:

• Highlight gists using gists API
• Highlight code directly from URL

Usage

import { HighlightPlusModule } from 'ngx-highlightjs/plus';
 
@NgModule({
  imports: [
    HighlightPlusModule
  ]
})
export class AppModule {
}

Highlight a gist file

1. Use [gist] directive with the gist id to get the response through the output (gistLoaded).
2. Once (gistLoaded) emits, you will get access to the gist response.
3. Use gistContent pipe to extract the file content from gist response using gist file name.

Example:

<pre [gist]="gistId" (gistLoaded)="gist = $event">
  <code [highlight]="gist | gistContent: 'main.js'"></code>
</pre>

Highlight all gist files

To loop over gist?.files, use keyvalue pipe to pass file name into gistContent pipe.

Example:

<ng-container [gist]="gistId" (gistLoaded)="gist = $event">
  <pre *ngFor="let file of gist?.files | keyvalue">
    <code [highlight]="gist | gistContent: file.key"></code>
  </pre>
</ng-container>

Highlight code from URL directly

Use the pipe codeFromUrl with the async pipe together to get the code text from a raw URL.

Example:

<pre>
  <code [highlight]="codeUrl | codeFromUrl | async"></code>
</pre>

Development

This project uses Angular CLI to build the package.

$ ng build ngx-highlightjs

Issues

If you identify any errors in the library, or have an idea for an improvement, please open an issue.

Author

Murhaf Sousli

• github/murhafsousli
• twitter/murhafsousli

More plugins

• ngx-scrollbar
• ngx-sharebuttons
• ngx-gallery
• ngx-progressbar
• ngx-scrollbar
• ngx-bar-rating
• ngx-disqus
• ngx-wordpress
• ngx-highlightjs
• ngx-teximate

Changelog

4.0.0

• feat: Lazy-load hljs library, closes #89 in 8cdba13.
• feat: Lazy-load languages scripts, in 952f33c.
• feat: Gist directive, closes #90 in 8b4c8fc.
• feat: Highlight code directly from URL, closes #91 in 5fa3c59.
• feat: Line numbers, closes #35 in c19b878.
• enhance: Move highlight.js package from peerDependencies to dependencies
• fix: Check if [highlight] input got undefined value, closes #81 in f2b14bd.
• fix: Add test files, closes #79 in 2913d05.

Breaking Changes

• Since the core library highlight.js will be lazy-loaded, all hljs functions in HighlightJS will return observables to make sure the library is loaded before execution.
• HighlightChildren directive has been deprecated.
• The global options languages property NgScrollOptions.languages type has changed.
• HighlightModule.forRoot() is deprecated, the highlight global options can be set using the injection token HIGHLIGHT_OPTIONS