ngx-annotate-text

This Angular component library is perfect for tasks like visualizing named entity recognition, part of speech tagging, or annotating text datasets. It allows for interactively highlighting and annotating parts of text.

Features

• 👆 Interactively mark text ranges such as sentences, words, or parts of words.
• 🗑️ Easily remove existing annotations.
• 🎉 Purely based on CSS, with no use of SVGs or canvas.
• 🛠️ Customize annotation rendering with your own Angular components.

Demo

View and edit the live demo Angular app on codesandbox.io or look through the code of the demo app in ngx-annotate-text/src/app/.

Screen recording:

Usage

1. Install the NPM package:

   npm install ngx-annotate-text

2. Import the Angular module NgxAnnotateTextModule:

   import { BrowserModule } from "@angular/platform-browser";
   import { NgModule } from "@angular/core";
   
   import { AppComponent } from "./app.component";
   import { NgxAnnotateTextModule } from "ngx-annotate-text";
   
   @NgModule({
     declarations: [AppComponent],
     imports: [BrowserModule, NgxAnnotateTextModule],
     providers: [],
     bootstrap: [AppComponent],
   })
   export class AppModule {}

3. Add the component ngx-annotate-text to your template:

   <ngx-annotate-text
     [(annotations)]="annotations"
     [removable]="true"
     [text]="text"
     annotationClass="my-annotation"
     #annotateText
   >
   </ngx-annotate-text>

4. Create properties in your component class for the text to be annotated and an (empty) array of annotations:

   import { Component, ViewChild } from "@angular/core";
   import { Annotation, NgxAnnotateTextComponent } from "ngx-annotate-text";
   
   @Component({
     selector: "app-root",
     templateUrl: "./app.component.html",
     styleUrls: ["./app.component.css"],
   })
   export class AppComponent {
     text: string =
       "On August 1, we went on vacation to Barcelona, Spain. Our flight took off at 11:00 am.";
   
     annotations: Annotation[] = [
       new Annotation(3, 11, "Date", "#0069d9"),
       new Annotation(36, 45, "City", "#dc3545"),
       new Annotation(47, 52, "Country", "#28a745"),
       new Annotation(77, 85, "Time", "#5a6268"),
     ];
   }

5. Having set annotationClass="my-annotation", a custom CSS styling can be applied by combining ::ng-deep with the class selector .my-annotation, e.g., to remove the border-radius:

   ::ng-deep .my-annotation .annotation-parent,
   ::ng-deep .my-annotation .annotation-content {
     border-radius: 0rem !important;
   }

API - NgxAnnotateText

Inputs

Input	Description	Type	Default value
annotations	Represents the parts of the given text which shall be annotated.	Annotation[]	[]
annotationClass	An optional CSS class applied to all elements which wrap the annotated parts of the given text.	string|undefined	undefined
annotationRendererComponent	An optional Angular component that shall be used for rendering the annotation. By default, it uses the provided NgxAnnotationRendererComponent. You can implement your own annotation rendering component to customize the visualization of annotations. The custom component must implement the interface NgxAnnotationRendererComponentInterface.	NgxAnnotationRendererComponentInterface	NgxAnnotationRendererComponent
removable	Determines whether annotations shall have a small button in the top right corner so that the user can remove an annotation.	boolean	true
text	The text which shall be displayed and annotated.	string	empty string

Outputs

Output	Description	Type
annotationsChange	Emits the list of existing annotations after an element has been removed by the user.	EventEmitter<Annotation[]>
clickAnnotation	Emits the selected annotation when the user clicks on an annotation's box, the label or text.	EventEmitter<Annotation>
removeAnnotation	Emits the selected annotation when the user removes it by clicking the annotation's X button in the upper right corner.	EventEmitter<Annotation>

Methods

Method	Description	Return type
getCurrentTextSelection	Returns the start index and end index of the currently selected text range. Returns undefined if no text is currently selected.	`ISelection
isOverlappingWithExistingAnnotations	Returns true if the given text selection is (partially) overlapping with an existing annotation. Returns false otherwise.	boolean

Development

Recreate project from scratch

npm install -g @angular/cli@^18
ng new ngx-annotate-text-workspace
cd ngx-annotate-text-workspace/
ng generate library ngx-annotate-text
ng add angular-eslint@^18
ng g angular-eslint:add-eslint-to-project ngx-annotate-text-workspace
ng g angular-eslint:add-eslint-to-project ngx-annotate-text
npm install prettier --save-dev
ng build ngx-annotate-text
ng lint
ng test ngx-annotate-text

Build

Run ng build ngx-annotate-text to build the project. The build artifacts will be stored in the dist/ directory.

Running the demo app

Run ng serve --open to start the demo app in your browser.

Running linting tools

Run ng lint ngx-annotate-text to execute ESLint.

Running unit tests

Run ng test ngx-annotate-text --code-coverage to execute the unit tests via Karma. Don't forget to set the environment variable for where to find Chrome / Chromium like so: export CHROME_BIN=/snap/bin/chromium.

Publish library as an npm package

⚠️ Don't manually publish to npmjs.org, there is a pipeline that runs automatically when a new release is created.

ng build ngx-annotate-text --configuration production
cd dist/ngx-annotate-text
npm publish

Development server

Build the library in watch mode:

ng build ngx-annotate-text --watch

Run the Angular dev server:

ng serve --open

Navigate to http://localhost:4200/. The app will automatically reload if you change any of the source files.