Angular 2 Read More Directive

Question

I need to build a readmore directive in Angular2. What this directive will do is for collapse and expand long blocks of text with "Read more" and "Close" links. Not on the basis of the character count but on the basis of the specified max height.

<div read-more [maxHeight]="250px" [innerHTML]="item.details">
</div>

Can anyone please guide what would be the most reliable way to get/set the height of the element for this specific case.

Any guidelines on how this specific directive could be implemented would also be highly appreciated.

I need to build something like this https://github.com/jedfoster/Readmore.js

Solution:

With the help from Andzhik I am able to build the below component that meets my requirements.

import { Component, Input, ElementRef, AfterViewInit } from '@angular/core';

@Component({
    selector: 'read-more',
    template: `
        <div [innerHTML]="text" [class.collapsed]="isCollapsed" [style.height]="isCollapsed ? maxHeight+'px' : 'auto'">
        </div>
            <a *ngIf="isCollapsable" (click)="isCollapsed =! isCollapsed">Read {{isCollapsed? 'more':'less'}}</a>
    `,
    styles: [`
        div.collapsed {
            overflow: hidden;
        }
    `]
})
export class ReadMoreComponent implements AfterViewInit {

    //the text that need to be put in the container
    @Input() text: string;

    //maximum height of the container
    @Input() maxHeight: number = 100;

    //set these to false to get the height of the expended container 
    public isCollapsed: boolean = false;
    public isCollapsable: boolean = false;

    constructor(private elementRef: ElementRef) {
    }

    ngAfterViewInit() {
        let currentHeight = this.elementRef.nativeElement.getElementsByTagName('div')[0].offsetHeight;
       //collapsable only if the contents make container exceed the max height
        if (currentHeight > this.maxHeight) {
            this.isCollapsed = true;
            this.isCollapsable = true;
        }
    }
}

Usage:

<read-more [text]="details" [maxHeight]="250"></read-more>

If there could be any improvements, please feel free to suggest.

Answer 1

With the help from Andzhik I am able to build the below component that meets my requirements.

import { Component, Input, ElementRef, AfterViewInit } from '@angular/core';

@Component({
    selector: 'read-more',
    template: `
        <div [innerHTML]="text" [class.collapsed]="isCollapsed" [style.height]="isCollapsed ? maxHeight+'px' : 'auto'">
        </div>
            <a *ngIf="isCollapsable" (click)="isCollapsed =! isCollapsed">Read {{isCollapsed? 'more':'less'}}</a>
    `,
    styles: [`
        div.collapsed {
            overflow: hidden;
        }
    `]
})
export class ReadMoreComponent implements AfterViewInit {

    //the text that need to be put in the container
    @Input() text: string;

    //maximum height of the container
    @Input() maxHeight: number = 100;

    //set these to false to get the height of the expended container 
    public isCollapsed: boolean = false;
    public isCollapsable: boolean = false;

    constructor(private elementRef: ElementRef) {
    }

    ngAfterViewInit() {
        let currentHeight = this.elementRef.nativeElement.getElementsByTagName('div')[0].offsetHeight;
       //collapsable only if the contents make container exceed the max height
        if (currentHeight > this.maxHeight) {
            this.isCollapsed = true;
            this.isCollapsable = true;
        }
    }
}

Usage:

<read-more [text]="details" [maxHeight]="250"></read-more>

Answer 2

import { Component, Input,OnChanges} from '@angular/core';
@Component({    
    selector: 'read-more',
    template: `
        <div [innerHTML]="currentText"></div>
        <span *ngIf="showToggleButton">
            <a (click)="toggleView()">Read {{isCollapsed? 'more':'less'}}</a>
        </span>`
})

export class ReadMoreDirective implements OnChanges {

    @Input('text') text: string;
    @Input('maxLength') maxLength: number = 100;
    @Input('showToggleButton')showToggleButton:boolean;

    currentText: string;

    public isCollapsed: boolean = true;

    constructor(
        //private elementRef: ElementRef
    ) {

    }
    toggleView() {
        this.isCollapsed = !this.isCollapsed;
        this.determineView();
    }

    determineView() {

        if (this.text.length <= this.maxLength) {
            this.currentText = this.text;
            this.isCollapsed = false;
            return;
        }

        if (this.isCollapsed == true) {
            this.currentText = this.text.substring(0, this.maxLength) + "...";
        } else if(this.isCollapsed == false)  {
            this.currentText = this.text;
        }

    }

    ngOnChanges() {
        if(!this.validateSource(this.text)) {
            //throw 'Source must be a string.';
            console.error('Source must be a string.');
        }
        else{
            this.determineView();
        }
    }

    validateSource(s) {
        if(typeof s !== 'string') {
            return false;
        } else {
            return true;
        }
    }
}

and usage

<read-more [text]="this is test text" [maxLength]="10" [showToggleButton]="true"></read-more>

Answer 3

If you want to display the text to the maximum number of chars without cutting any word, change this line of code:

this.currentText = this.text.substring(0, this.maxLength) + "...";

To:

this.currentText = this.text.substring(0, this.maxLength);
this.currentText = this.currentText.substr(0, Math.min(this.currentText.length, this.currentText.lastIndexOf(" ")))
this.currentText = this.currentText + "..."

Answer 4

Again i solved these types of problem with dynamic data and full controlling.

 <div class="Basic-Info-para">
   <p>
     <span *ngIf="personalBasicModel.professionalSummary.length>200" id="dots"> 
         {{personalBasicModel.professionalSummary | slice:0:200}} ...
    </span>
     <span id="more">{{personalBasicModel.professionalSummary }}
</span>
 </p>
</div> 

Here , personalBasicModel.professionalSummary contain string . like any text.
slice:0:200 = use slice pipe for splice string with 200 character length . you can be change length according your requirement. id="dots" & id="more" two important thing.

<div class="Basic-Info-SeeMore">
            <button class="SeeMore"(click)="showMore(paasValueOn_SeeMoreBtn)">
                {{showLess_More}}
            </button>
        </div>

Here we define a button with dynamic text (see more and see less ) with click event.

//---------------------------------- ts file -----------------------------------//

Define variable

showLess_More : string = "SEE MORE...";
paasValueOn_SeeMoreBtn : boolean = true;

Event(Method) fire when user click on see more button

 showMore(data:boolean){
    if(data){
      $("#dots").css('display', 'none');
      $("#more").css('display', 'inline');
      this.showLess_More = "SEE LESS ...";
      this.paasValueOn_SeeMoreBtn = false;
    }else{
      $("#dots").css('display', 'inline');
      $("#more").css('display', 'none');
      this.showLess_More = "SEE MORE...";
      this.paasValueOn_SeeMoreBtn = true;

    }

  }

Answer 5

lineheight approach:-

lineheight and little calculation and some css text-overflow: ellipsis; does this job.

.css

.descLess {
  margin-bottom: 10px;
  text-overflow: ellipsis;
  overflow: hidden;
  word-wrap: break-word;
  display: -webkit-box;
  line-height: 1.8;      <==== adjust line-height...a/q to your need
  letter-spacing: normal;
  white-space: normal;
  max-height: 52px;  <==== 250px etc:-
  width: 100%;
  /* autoprefixer: ignore next */
  -webkit-line-clamp: 2; <==== clamp line 2...or 3 or 4 or 5...
  -webkit-box-orient: vertical;
}

.html

    <div class="col-12 rmpm">
          <div id="descLess" *ngIf="seeMoreDesc === 'false'" class="descLess col-12 rmpm">
                {{inputData?.desc}}
           </div>
        <div *ngIf="seeMoreDesc === 'true'" class="col-12 rmpm" style="margin-bottom: 10px;line-height: 1.8;"> 
   <!--Use Line height here-->
                {{inputData?.desc}}
               </div>
        <span class="seeMore" *ngIf="seeMoreDesc === 'false' && lineHeightDesc > 21"
             (click)="updateSeeMore('seeMoreDesc', 'true')">
                 See More
        </span>
        <span class="seeMore" *ngIf="seeMoreDesc === 'true'"
               (click)="updateSeeMore('seeMoreDesc', 'false')">
                   See Less
        </span>
         </div>

.ts

declare const $:any;
seeMoreDesc = 'false';
seeMore = '';
inputData = {
   'desc':'Lorem Ipusme dummy text..................'
 }
 constructor(
        private eRef: ElementRef,
        private cdRef : ChangeDetectorRef
    ) {}
    ngAfterViewChecked() {
       // pass line height here
        this.lineHeightDesc = (Number($('#descLess').height()) / 1.8);
        this.cdRef.detectChanges();
    }


     public updateSeeMore(type, action) {
         if (type === 'seeMoreDesc') {
               this.seeMoreDesc = action;
                this.cdRef.detectChanges();
            } else if (type === 'seeMore') {
                this.seeMore = action;
                this.cdRef.detectChanges();
            }

        }

Answer 6

I think you'll need a Component rather then Directive. Components makes more sense since you need to add Read more button/link, i.e. update DOM.

@Component({
    selector: 'read-more',
    template: `
        <div [class.collapsed]="isCollapsed">
            <ng-content></ng-content>
        </div>
        <div (click)="isCollapsed = !isCollapsed">Read more</div>
    `,
    styles: [`
        div.collapsed {
            height: 250px;
            overflow: hidden;
        }
    `]
})

export class ReadMoreComponent {
    isCollapsed = true;
}

Usage:

<read-more>
   <!-- you HTML goes here -->
</read-more>