@avtest/ng-spy
v5.0.6
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A lightweight, dependency-free scrollspy for angular. Use this library to spy on HTML elements on your page when the window is scrolled or resized.
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ng-spy
A lightweight, dependency-free scrollspy for angular. Use this library to spy on HTML elements on your page when the window is scrolled or resized.
This library provides directives and services to help you subscribe to new elements entering the browser window and possibly adds or remove CSS classes to these elements.
This library does not provide utilities to scrollTo
spied elements and certainly does not handle link clicks. You have to handle these on your own.
Table of Contents
Example
Code for the previous example is also in this repository under the src folder.
Usage
npm install --save ng-spy
Import the module
@NgModule({ declarations: [], imports: [ // ... ScrollSpyModule ], providers: [], bootstrap: [AppComponent] }) export class AppModule { }
In your container component:
ngAfterViewInit() { this.spyService.spy({ thresholdBottom: 50 }); }
Use
SpyTarget
directive to mark element as a target:<h1 spyTarget="target-1">Hello, World!!</h1>
Optional: Use
SpyOn
directive to spy on a target:<a spyOn="target-1" activeClass="navbar__link--active" class="navbar__link" href="#target-1">target 1</a>
Alternatively, you can subscribe to
activeSpyTarget
fromScrollSpyService
, which will emit every time a new element is active.this.scrollspyService.activeSpyTarget.subscribe( (activeTargetName: string) => console.log(activeTargetName) );
To start multiple spys you can scope the
ScrollSpyService
to a specific component or module in theproviders
array.// In component or module metadata: { // ... providers: [ ScrollSpyService ] }
Documentation
Directives
SpyOn
A directive to spy on a previously added target.
Input
| Name | Type | Description | Default value | |:-----------: |:------: |:---------------------------------------------------: |:-------------: | | activeClass | string | a class to be added to host element if it is active | | | spyOn | string | the name of the target to spy on | |
SpyTarget
A directive to mark an element as a spy target.
Input
| Name | Type | Description | Default value |
|:---------: |:------: |:---------------------------------------------------------------------------------------------------------------: |:-------------: |
| spyTarget | string | the name of the target to be added. This also adds an id attribute to the host element with the spyTarget
value | |
Services
ScrollSpyService
Functions
spy(spyOptions: SpyOptions): void
Starts spying on the targets. Call this on the top level container of your targets in AfterViewInit
lifecycle hook. Without calling this function, nothing will happen.
Parameters:
| Name | Type | Optional? | Description | Default value | |:----------: |:----------: |----------- |:----------------------------------------------------------------------------: |:------------------------------------------: | | spyOptions | SpyOptions | Yes | Options to override some default behaviors. See SpyOptions for more details. | { thresholdTop = 0 , thresholdBottom = 0 } |
addTarget(target: SpyTarget): void
adds the target
to the targets collection for spying. This action will also trigger a check to re-evaluate the active target.
Parameters:
| Name | Type | Optional? | Description | Default value | |:------: |:---------: |----------- |:----------------------: |:-------------: | | target | SpyTarget | No | The target to be added. | |
removeTarget(target: string): void
Removes a previously added target from the targets collection. This action will also trigger a check to re-evaluate the active target.
Parameters:
| Name | Type | Optional? | Description | Default value | |:------: |:------: |----------- |:-----------------------------: |:-------------: | | target | string | No | The target name to be removed | |
checkActiveElement(scrollContainer?: ElementRef): void
Tries to find the active target in the targets collection. If found it will emit the target name using the activeSpyTarget
observable, Otherwise it will emit null.
Parameters:
| Name | Type | Optional? | Description | Default value | |:---------------: |:----------: |----------- |:-------------------------------------------------------: |:-------------: | | scrollContainer | ElementRef | Yes | The scroll container in which your targets are present. | |
isElementActive(element: ElementRef, scrollContainer?: ElementRef, currentActiveElement?: ElementRef): boolean
Checks if the element
is inside the browser window and optionally inside the scrollContainer
.
If a currentActiveElement
is provided, it will also check if the element
's offsetTop is greater than the currentActiveElement
. Meaning, if two targets are active, only the last one on the screen will be emitted.
If a scrollContainer
is provided, it will ignore thresholdBottom
and thresholdTop
in the window check and will instead check for the threshold inside the scrollContainer
.
Parameters:
| Name | Type | Optional? | Description | Default value | |:--------------------: |:----------: |----------- |:-------------------------------------------------: |:-------------: | | element | ElementRef | No | The element to be checked. | | | scrollContainer | ElementRef | Yes | The scroll container which the element is inside. | | | currentActiveElement | ElementRef | Yes | An element that is guaranteed to be active. | |
stopSpying(): void
Stops spying on the targets, completes the activeSpyTarget
subject and clears the targets collection.
Getters
activeSpyTarget: Observable<string>
Use this to subscribe to new active spy targets. Value can be null
if no target is found to be active.
Interfaces
SpyOptions
| Name | Type | Optional? | Description |
|:---------------: |:----------: |----------- |:-----------------------------------------------------------------------------------------: |
| scrollContainer | ElementRef | Yes | The scroll container in which your targets are present. |
| thresholdTop | number | Yes | A number added to the top of your scroll container while checking in isElementActive
|
| thresholdBottom | number | Yes | A number added to the bottom of your scroll container while checking in isElementActive
|
SpyTarget
| Name | Type | Optional? | Description | |:-------: |:----------: |----------- |:----------------------------------------------------------------------------------------------------------------: | | name | string | No | The name of the spy target. This is also may be used as an id for the html element. So make sure this is unique. | | element | ElementRef | No | A reference to the target element. |
InjectionTokens
RESIZE_TIME_THRESHOLD
Used in the resize event with auditTime
.
Default Value: 300
SCROLL_TIME_THRESHOLD
Used in the scroll events with auditTime
.
Default Value: 10