ng2-page-scroll

Animated "scroll to element" functionality written in pure angular2 with no additional dependencies

Features

• easy-to-use directive: scroll to an element referenced in the href-attribute (href="#mytarget) just by adding pageScroll directive
• service usage: trigger scroll animations from your component or when server responds
• customizable: adjust duration, offset or whether scrolling stops if the user interrupts (read more)
• use custom easing functions to calculate the scroll position over time
• works across routes (scrolls to target element as soon as the routing has finished) and in both directions (horizontal/vertical)

Table of contents

• Setup
• Usage
  • Directive
  • Service
• Configuration
• Directive API
• Example app

Setup

First you need to install the npm module:

npm install ng2-page-scroll --save

Then add the Ng2PageScrollModule to the imports array of your application module:

import {Ng2PageScrollModule} from 'ng2-page-scroll';

@NgModule({
    imports: [
        /* Other imports here */
        Ng2PageScrollModule.forRoot()
        ]
})
export class AppModule {
}

To ensure there's only one instance of a PageScrollService (Singleton) it is recommended to add the PageScrollService to only one Injector, preferably the root injector of the application. You may read more about angular 2 dependency injection hierarchy at their documentation.

Finally you need to specify how your application should load the ng2-page-scroll library:

Angular2 modules

All the compiled JavaScript files use ES2015 module format, so they are ready for usage with RollupJS. However, you cannot use them with SystemJS.

.metadata.json files are generated for usage with Angular2 AoT compiler.

SystemJS

UMD bundles are available for SystemJS loading. Example:

System.config({
    paths: {
        'npm:': 'node_modules/'
    },
    map: {
        app: 'app',

        '@angular/core'   : 'npm:@angular/core/bundles/core.umd.js',
        '@angular/common' : 'npm:@angular/common/bundles/common.umd.js',
        // further angular bundles...

        'ng2-page-scroll/ng2-page-scroll': 'npm:ng2-page-scroll/bundles/ng2-page-scroll.umd.js',

        rxjs: 'npm:rxjs',
    },
    packages: {
        app : {defaultExtension: 'js', main: './main.js'},
        rxjs: {defaultExtension: 'js'}
    }
});

import {Ng2PageScrollModule} from 'ng2-page-scroll/ng2-page-scroll';

@NgModule({
    imports: [
        /* Other imports here */
        Ng2PageScrollModule.forRoot()
        ]
})
export class AppModule {
}

Usage

Directive

In your template you may add the pageScroll attribute to elements with an href attribute pointing towards an id on the same page (e.g. #theId).

@Component({
   ...
   template: `...
        <a pageScroll href="#awesomePart">Take me to the awesomeness</a>
        <!-- Further content here -->
        <h2 id="awesomePart">This is where the awesome happens</h2>
   ...`,
})
export class MyComponent {
}

Service

You may use the service for more advanced scroll animations. Using the service you may trigger scroll animations on any custom event or more complex configuration. Possible use cases are server responses or after content initialization.

Start by obtaining a reference to the PageScrollService instance by adding it to your component's constructor. The PageScrollService offers a start() method to trigger PageScrollInstances. A PageScrollInstance is an object encapsulating all information relevant for performing a scroll animation. You may create a new PageScrollInstance by using the provided factory methods PageScrollInstance#simpleInstance, PageScrollInstance#simpleInlineInstance, and PageScrollInstance#advancedInstance.

@Component({
    template: `
        <p>Main content</p>
        <!-- Further content here -->
        <h2 id="head2">Part in a container</h2>
        <div #container>
            <p>Container content</p>
            <h3 id="head3">Heading</h3>
        </div>`
})
export class MyComponent {

     @ViewChild('container')
     private container: ElementRef;

     constructor(private pageScrollService: PageScrollService, @Inject(DOCUMENT) private document: Document) {
     }

     public goToHead2(): void {
         let pageScrollInstance: PageScrollInstance = PageScrollInstance.simpleInstance(this.document, '#head2');
         this.pageScrollService.start(pageScrollInstance);
     };    
     
     public scrollSomewhereHorizontally(): void {
         let pageScrollInstance: PageScrollInstance = PageScrollInstance.simpleDirectionInstance(this.document, '#targetToTheRight', true);
         this.pageScrollService.start(pageScrollInstance);
     }; 

     public goToHeadingInContainer(): void {
         let pageScrollInstance: PageScrollInstance = PageScrollInstance.simpleInlineInstance(this.document, '#head3', this.container.nativeElement);
         this.pageScrollService.start(pageScrollInstance);
     };
 }

Configuration

The class PageScrollConfig offers static properties to be manipulated to configure the default behavior. Override the respective properties to change all page scroll-animation defaults.

Configuration Option	Type	Default	Description
defaultScrollOffset	number	0	Pixels to offset from the top of the element when scrolling to (positive value = scrolling will stop given pixels atop the target element).
defaultIsVerticalScrolling	boolean	true	Whether the scroll should happen to the target element in vertical direction (true, default) or horizontal (false)
defaultDuration	number	1250	Duration in milliseconds the whole scroll-animation should last.
defaultInterruptible	boolean	true	Whether the scroll animation should stop if the user interferes with it (true) or not (false).
defaultEasingLogic	EasingLogic	linearEasing	Easing method to be used while calculating the scroll position over time (default is linear easing).

Example

import {PageScrollConfig} from 'ng2-page-scroll';

export class AppComponent {
    constructor() {
        PageScrollConfig.defaultScrollOffset = 50;
        PageScrollConfig.defaultEasingLogic = {
            ease: (t: number, b: number, c: number, d: number): number => {
                // easeInOutExpo easing
                if (t === 0) return b;
                if (t === d) return b + c;
                if ((t /= d / 2) < 1) return c / 2 * Math.pow(2, 10 * (t - 1)) + b;
                return c / 2 * (-Math.pow(2, -10 * --t) + 2) + b;
            }
        };
    }
}

Directive API

Additional attributes may be set on an DOM element using the pageScroll directive for customization. They take precedence over the default settings specified in PageScrollConfig class. Thereby it is possible to have all page scroll-animations last e.g. 2 seconds, but a specific one should be performed with a custom easing function and a duration of only 1 second.

PageScroll properties

Attribute	Type	Default	Description
pageScroll			Attribute adding scroll-animation behavior when the click-event happens on the element.
pageScrollHorizontal	boolean	false	Whether the scroll should happen in vertical direction (false, default) or horizontal (true).
pageScrollOffset	number	0	Pixels to offset from the top of the element when scrolling to (positive value = scrolling will stop given pixels atop the target element).
pageScrollDuration	number	1250	Duration in milliseconds the whole scroll-animation should last.
pageScrollInterruptible	boolean	true	Whether the scroll animation should stop if the user interferes with it (true) or not (false).
pageScrollEasing	EasingLogic	linearEasing	Easing method to be used while calculating the scroll position over time (default is linear easing).

PageScroll events

Event	Type	Description
pageScrollFinish	boolean	Fired when the scroll-animation stops. Emits a boolean value which indicates whether the scroll animation finished successfully and reached its target (true) or not (false). Possible reasons for false: target not found or interrupted due to another scroll animation starting or user interaction.

Example

The following example will check whether the route Home is currently loaded. If this is true, the scroll-animation will be performed with the default properties. If a different route is loaded, a subscription for route changes will be made and the scroll-animation will be performed as soon as the new route is loaded.

 <a pageScroll [routerLink]="['Home']" href="#myanchor">Go there</a>

Overriding all possible properties. doSmth() and myEasing are defined in the component

 <a pageScroll [pageScrollOffset]="0" [pageScrollDuration]="2000" [pageScrollEasing]="myEasing" [pageScrollInterruptible]="false" (pageScrollFinish)="doSmth($event)" href="#theanchor">Visit</a>

    myEasing: EasingLogic = {
        ease: (t: number, b: number, c: number, d: number): number => {
            // easeInOutExpo easing
            if (t === 0) return b;
            if (t === d) return b + c;
            if ((t /= d / 2) < 1) return c / 2 * Math.pow(2, 10 * (t - 1)) + b;
            return c / 2 * (-Math.pow(2, -10 * --t) + 2) + b;
        }
    };

    doSmth(reachedTarget: boolean): void {
        if (reachedTarget) {
            console.log('Yeah, we reached our destination');
        } else {
            console.log('Ohoh, something interrupted us');
        }
    }

Using the right scrolling view

By default the scrollTop property of the body and html element are manipulated. Although this works in most situations, depending on your HTML structure and css setup, the DOM element that is actually scrollable may not be one of these two default ones. In these situations no scroll animation will be visible at first. Create a PageScrollInstances with an adjusted scrollingView (e.g. using PageScrollInstances#simpleInlineInstance factory method) and trigger that via PageScrollService#start. An example is given in the PageScrollService section and on the "nested scrolling" page in the demo application.

To get the scrollTop value of a certain DOM element, you may use the Chrome Developer Tools: highlight the element in the "Elements" tab and execute $0.scrollTop in the developer console.

Example App

The demo subfolder contains a project created with angular-cli that has been adapted to showcase the functionality of ng2-page-scroll. Run the demo app by checking out that repository and execute the following command in the project root directory:

npm run demo

This will perform the following steps:

// Install the ng2-page-scroll project
npm install
// Change into the example website folder
cd demo/
// Uninstall the current ng2-page-scroll version
npm uninstall ng2-page-scroll
// Install the demo website's dependencies
npm install
// Run the server
ng serve

TODO:

• Test across browsers

License

MIT