August 23 2016

Angular 2 - Pagination Example with Logic like Google

November 18 2016 - Updated to Angular 2.2.1

This is an example of how to implement pagination in Angular 2 and TypeScript with logic like Google's search results.

Project is available on GitHub at https://github.com/cornflourblue/angular2-pagination-example.

Here it is in action: (See on Plunker at http://plnkr.co/edit/vPXf2U?p=preview)

Update History:
  • 18 Nov 2016 - Updated to Angular 2.2.1 and moved dummy data from client side array to json file on the server to show how to paginate items from api call
  • 21 Sep 2016 - Updated to Angular 2.0 Final


To see the same example in Angular 1 you can check out AngularJS - Pagination Example with Logic like Google.


Google's Pagination Logic

The logic in Google's pagination is as follows:

  • there are 10 page links shown at any time (e.g. 1 2 3 4 5 6 7 8 9 10) unless there are less than 10 total pages
  • the active link (current page) is in the 6th position, except for when the active link is below 6 or less than 4 from the last position


Here's what it looks like for each page if there are 15 total pages:

[1] 2 3 4 5 6 7 8 9 10
1 [2] 3 4 5 6 7 8 9 10
1 2 [3] 4 5 6 7 8 9 10
1 2 3 [4] 5 6 7 8 9 10
1 2 3 4 [5] 6 7 8 9 10
1 2 3 4 5 [6] 7 8 9 10
2 3 4 5 6 [7] 8 9 10 11
3 4 5 6 7 [8] 9 10 11 12
4 5 6 7 8 [9] 10 11 12 13
5 6 7 8 9 [10] 11 12 13 14
6 7 8 9 10 [11] 12 13 14 15
6 7 8 9 10 11 [12] 13 14 15
6 7 8 9 10 11 12 [13] 14 15
6 7 8 9 10 11 12 13 [14] 15
6 7 8 9 10 11 12 13 14 [15] 


Running the Angular 2 Example Locally

I used the Angular 2 quickstart project as a base for the application, it's written in TypeScript and uses systemjs for loading modules. If you're new to angular 2 I'd recommend checking out the quickstart as it provides details on the project tooling and configuration files which aren't covered in this post.

  1. Install NodeJS (> v4) and NPM (> v3) from https://nodejs.org/en/download/, you can check the versions you have installed by running node -v and npm -v from the command line.
     
  2. Download the project source code from https://github.com/cornflourblue/angular2-pagination-example
     
  3. Install all required npm packages by running npm install from the command line in the project root folder (where the package.json is located).
     
  4. Start the application by running npm start from the command line in the project root folder.


Angular 2 Pager Service - Pagination Logic in TypeScript like Google

To make it easy to reuse the pagination logic in different Angular 2 components or modules, I wrapped the pagination logic in an angular 2 service.

import * as _ from 'underscore';

export class PagerService {
    getPager(totalItems: number, currentPage: number = 1, pageSize: number = 10) {
        // calculate total pages
        let totalPages = Math.ceil(totalItems / pageSize);

        let startPage: number, endPage: number;
        if (totalPages <= 10) {
            // less than 10 total pages so show all
            startPage = 1;
            endPage = totalPages;
        } else {
            // more than 10 total pages so calculate start and end pages
            if (currentPage <= 6) {
                startPage = 1;
                endPage = 10;
            } else if (currentPage + 4 >= totalPages) {
                startPage = totalPages - 9;
                endPage = totalPages;
            } else {
                startPage = currentPage - 5;
                endPage = currentPage + 4;
            }
        }

        // calculate start and end item indexes
        let startIndex = (currentPage - 1) * pageSize;
        let endIndex = Math.min(startIndex + pageSize - 1, totalItems - 1);

        // create an array of pages to ng-repeat in the pager control
        let pages = _.range(startPage, endPage + 1);

        // return object with all pager properties required by the view
        return {
            totalItems: totalItems,
            currentPage: currentPage,
            pageSize: pageSize,
            totalPages: totalPages,
            startPage: startPage,
            endPage: endPage,
            startIndex: startIndex,
            endIndex: endIndex,
            pages: pages
        };
    }
}


Angular 2 AppComponent that uses the Pager Service 

An example angular 2 component that uses the above pager service to paginate a list of dummy items that are pulled from a json file on the server.

import { Component, OnInit } from '@angular/core';
import { Http, Headers, RequestOptions, Response } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/map'

import * as _ from 'underscore';

import { PagerService } from './_services/index'

@Component({
    moduleId: module.id,
    selector: 'app',
    templateUrl: 'app.component.html'
})

export class AppComponent implements OnInit {
    constructor(private http: Http, private pagerService: PagerService) { }

    // array of all items to be paged
    private allItems: any[];

    // pager object
    pager: any = {};

    // paged items
    pagedItems: any[];

    ngOnInit() {
        // get dummy data
        this.http.get('./dummy-data.json')
            .map((response: Response) => response.json())
            .subscribe(data => {
                // set items to json response
                this.allItems = data;

                // initialize to page 1
                this.setPage(1);
            });
    }

    setPage(page: number) {
        if (page < 1 || page > this.pager.totalPages) {
            return;
        }

        // get pager object from service
        this.pager = this.pagerService.getPager(this.allItems.length, page);

        // get current page of items
        this.pagedItems = this.allItems.slice(this.pager.startIndex, this.pager.endIndex + 1);
    }
}


Angular 2 HTML Template with paged items and pager navigation

An example angular 2 template that shows a list of paged items and the pagination links for navigating between pages.

<div>
    <div class="container">
        <div class="text-center">
            <h1>Angular 2 - Pagination Example with logic like Google</h1>

            <!-- items being paged -->
            <div *ngFor="let item of pagedItems">{{item.name}}</div>

            <!-- pager -->
            <ul *ngIf="pager.pages && pager.pages.length" class="pagination">
                <li [ngClass]="{disabled:pager.currentPage === 1}">
                    <a (click)="setPage(1)">First</a>
                </li>
                <li [ngClass]="{disabled:pager.currentPage === 1}">
                    <a (click)="setPage(pager.currentPage - 1)">Previous</a>
                </li>
                <li *ngFor="let page of pager.pages" [ngClass]="{active:pager.currentPage === page}">
                    <a (click)="setPage(page)">{{page}}</a>
                </li>
                <li [ngClass]="{disabled:pager.currentPage === pager.totalPages}">
                    <a (click)="setPage(pager.currentPage + 1)">Next</a>
                </li>
                <li [ngClass]="{disabled:pager.currentPage === pager.totalPages}">
                    <a (click)="setPage(pager.totalPages)">Last</a>
                </li>
            </ul>
        </div>
    </div>
</div>


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