Simple pagination in javascript

I created a class structure for collections in general that would meet this requirement. and it looks like this:

class Collection {

    constructor() {
        this.collection = [];
        this.index = 0;
    }

    log() {
        return console.log(this.collection);
    }

    push(value) {
        return this.collection.push(value);
    }

    pushAll(...values) {
        return this.collection.push(...values);
    }

    pop() {
        return this.collection.pop();
    }

    shift() {
        return this.collection.shift();
    }

    unshift(value) {
        return this.collection.unshift(value);
    }

    unshiftAll(...values) {
        return this.collection.unshift(...values);
    }

    remove(index) {
        return this.collection.splice(index, 1);
    }

    add(index, value) {
        return this.collection.splice(index, 0, value);
    }

    replace(index, value) {
        return this.collection.splice(index, 1, value);
    }

    clear() {
        this.collection.length = 0;
    }

    isEmpty() {
        return this.collection.length === 0;
    }

    viewFirst() {
        return this.collection[0];
    }

    viewLast() {
        return this.collection[this.collection.length - 1];
    }

    current(){
        if((this.index <= this.collection.length - 1) && (this.index >= 0)){
            return this.collection[this.index];
        }
        else{
            return `Object index exceeds collection range.`;
        }
    }

    next() {
        this.index++;
        this.index > this.collection.length - 1 ? this.index = 0 : this.index;
        return this.collection[this.index];
    }

    previous(){
        this.index--;
        this.index < 0 ? (this.index = this.collection.length-1) : this.index;
        return this.collection[this.index];
    }
}

...and essentially what you would do is have a collection of arrays of whatever length for your pages pushed into the class object, and then use the next() and previous() functions to display whatever 'page' (index) you wanted to display. Would essentially look like this:

let books = new Collection();
let firstPage - [['dummyData'], ['dummyData'], ['dummyData'], ['dummyData'], ['dummyData'],];
let secondPage - [['dumberData'], ['dumberData'], ['dumberData'], ['dumberData'], ['dumberData'],];
books.pushAll(firstPage, secondPage); // loads each array individually
books.current() // display firstPage
books.next() // display secondPage

I'll address any questions you have... but here is an improved pattern you should follow to reduce code duplication.

As a sidenote though, you should consider not doing pagination on client-side. Since if you have a huge dataset, it would mean you need to download all the data before your page loads. Better to implement server-side pagination instead.

Fiddle: http://jsfiddle.net/Lzp0dw83/

HTML

<div id="listingTable"></div>
<a href="javascript:prevPage()" id="btn_prev">Prev</a>
<a href="javascript:nextPage()" id="btn_next">Next</a>
page: <span id="page"></span>

Javascript (put anywhere):

var current_page = 1;
var records_per_page = 2;

var objJson = [
    { adName: "AdName 1"},
    { adName: "AdName 2"},
    { adName: "AdName 3"},
    { adName: "AdName 4"},
    { adName: "AdName 5"},
    { adName: "AdName 6"},
    { adName: "AdName 7"},
    { adName: "AdName 8"},
    { adName: "AdName 9"},
    { adName: "AdName 10"}
]; // Can be obtained from another source, such as your objJson variable

function prevPage()
{
    if (current_page > 1) {
        current_page--;
        changePage(current_page);
    }
}

function nextPage()
{
    if (current_page < numPages()) {
        current_page++;
        changePage(current_page);
    }
}

function changePage(page)
{
    var btn_next = document.getElementById("btn_next");
    var btn_prev = document.getElementById("btn_prev");
    var listing_table = document.getElementById("listingTable");
    var page_span = document.getElementById("page");

    // Validate page
    if (page < 1) page = 1;
    if (page > numPages()) page = numPages();

    listing_table.innerHTML = "";

    for (var i = (page-1) * records_per_page; i < (page * records_per_page); i++) {
        listing_table.innerHTML += objJson[i].adName + "<br>";
    }
    page_span.innerHTML = page;

    if (page == 1) {
        btn_prev.style.visibility = "hidden";
    } else {
        btn_prev.style.visibility = "visible";
    }

    if (page == numPages()) {
        btn_next.style.visibility = "hidden";
    } else {
        btn_next.style.visibility = "visible";
    }
}

function numPages()
{
    return Math.ceil(objJson.length / records_per_page);
}

window.onload = function() {
    changePage(1);
};

UPDATE 2014/08/27

There is a bug above, where the for loop errors out when a particular page (the last page usually) does not contain records_per_page number of records, as it tries to access a non-existent index.

The fix is simple enough, by adding an extra checking condition into the for loop to account for the size of objJson:

Updated fiddle: http://jsfiddle.net/Lzp0dw83/1/

for (var i = (page-1) * records_per_page; i < (page * records_per_page) && i < objJson.length; i++)

Below is the pagination logic as a function


function Pagination(pageEleArr, numOfEleToDisplayPerPage) {
    this.pageEleArr = pageEleArr;
    this.numOfEleToDisplayPerPage = numOfEleToDisplayPerPage;
    this.elementCount = this.pageEleArr.length;
    this.numOfPages = Math.ceil(this.elementCount / this.numOfEleToDisplayPerPage);
    const pageElementsArr = function (arr, eleDispCount) {
        const arrLen = arr.length;
        const noOfPages = Math.ceil(arrLen / eleDispCount);
        let pageArr = [];
        let perPageArr = [];
        let index = 0;
        let condition = 0;
        let remainingEleInArr = 0;

        for (let i = 0; i < noOfPages; i++) {

            if (i === 0) {
                index = 0;
                condition = eleDispCount;
            }
            for (let j = index; j < condition; j++) {
                perPageArr.push(arr[j]);
            }
            pageArr.push(perPageArr);
            if (i === 0) {
                remainingEleInArr = arrLen - perPageArr.length;
            } else {
                remainingEleInArr = remainingEleInArr - perPageArr.length;
            }

            if (remainingEleInArr > 0) {
                if (remainingEleInArr > eleDispCount) {
                    index = index + eleDispCount;
                    condition = condition + eleDispCount;
                } else {
                    index = index + perPageArr.length;
                    condition = condition + remainingEleInArr;
                }
            }
            perPageArr = [];
        }
        return pageArr;
    }
    this.display = function (pageNo) {
        if (pageNo > this.numOfPages || pageNo <= 0) {
            return -1;
        } else {
            console.log('Inside else loop in display method');
            console.log(pageElementsArr(this.pageEleArr, this.numOfEleToDisplayPerPage));
            console.log(pageElementsArr(this.pageEleArr, this.numOfEleToDisplayPerPage)[pageNo - 1]);
            return pageElementsArr(this.pageEleArr, this.numOfEleToDisplayPerPage)[pageNo - 1];
        }
    }
}

const p1 = new Pagination(['a', 'b', 'c', 'd', 'e', 'f', 'g'], 3);
console.log(p1.elementCount);
console.log(p1.pageEleArr);
console.log(p1.numOfPages);
console.log(p1.numOfEleToDisplayPerPage);
console.log(p1.display(3));

A simple client-side pagination example where data is fetched only once at page loading.

// dummy data
        const myarr = [{ "req_no": 1, "title": "test1" },
        { "req_no": 2, "title": "test2" },
        { "req_no": 3, "title": "test3" },
        { "req_no": 4, "title": "test4" },
        { "req_no": 5, "title": "test5" },
        { "req_no": 6, "title": "test6" },
        { "req_no": 7, "title": "test7" },
        { "req_no": 8, "title": "test8" },
        { "req_no": 9, "title": "test9" },
        { "req_no": 10, "title": "test10" },
        { "req_no": 11, "title": "test11" },
        { "req_no": 12, "title": "test12" },
        { "req_no": 13, "title": "test13" },
        { "req_no": 14, "title": "test14" },
        { "req_no": 15, "title": "test15" },
        { "req_no": 16, "title": "test16" },
        { "req_no": 17, "title": "test17" },
        { "req_no": 18, "title": "test18" },
        { "req_no": 19, "title": "test19" },
        { "req_no": 20, "title": "test20" },
        { "req_no": 21, "title": "test21" },
        { "req_no": 22, "title": "test22" },
        { "req_no": 23, "title": "test23" },
        { "req_no": 24, "title": "test24" },
        { "req_no": 25, "title": "test25" },
        { "req_no": 26, "title": "test26" }];

        // on page load collect data to load pagination as well as table
        const data = { "req_per_page": document.getElementById("req_per_page").value, "page_no": 1 };

        // At a time maximum allowed pages to be shown in pagination div
        const pagination_visible_pages = 4;


        // hide pages from pagination from beginning if more than pagination_visible_pages
        function hide_from_beginning(element) {
            if (element.style.display === "" || element.style.display === "block") {
                element.style.display = "none";
            } else {
                hide_from_beginning(element.nextSibling);
            }
        }
        
        // hide pages from pagination ending if more than pagination_visible_pages
        function hide_from_end(element) {
            if (element.style.display === "" || element.style.display === "block") {
                element.style.display = "none";
            } else {
                hide_from_beginning(element.previousSibling);
            }
        }
        
        // load data and style for active page
        function active_page(element, rows, req_per_page) {
            var current_page = document.getElementsByClassName('active');
            var next_link = document.getElementById('next_link');
            var prev_link = document.getElementById('prev_link');
            var next_tab = current_page[0].nextSibling; 
            var prev_tab = current_page[0].previousSibling;
            current_page[0].className = current_page[0].className.replace("active", "");
            if (element === "next") {
                if (parseInt(next_tab.text).toString() === 'NaN') {
                    next_tab.previousSibling.className += " active";
                    next_tab.setAttribute("onclick", "return false");
                } else {
                    next_tab.className += " active"
                    render_table_rows(rows, parseInt(req_per_page), parseInt(next_tab.text));
                    if (prev_link.getAttribute("onclick") === "return false") {
                        prev_link.setAttribute("onclick", `active_page('prev',\"${rows}\",${req_per_page})`);
                    }
                    if (next_tab.style.display === "none") {
                        next_tab.style.display = "block";
                        hide_from_beginning(prev_link.nextSibling)
                    }
                }
            } else if (element === "prev") {
                if (parseInt(prev_tab.text).toString() === 'NaN') {
                    prev_tab.nextSibling.className += " active";
                    prev_tab.setAttribute("onclick", "return false");
                } else {
                    prev_tab.className += " active";
                    render_table_rows(rows, parseInt(req_per_page), parseInt(prev_tab.text));
                    if (next_link.getAttribute("onclick") === "return false") {
                        next_link.setAttribute("onclick", `active_page('next',\"${rows}\",${req_per_page})`);
                    }
                    if (prev_tab.style.display === "none") {
                        prev_tab.style.display = "block";
                        hide_from_end(next_link.previousSibling)
                    }
                }
            } else {
                element.className += "active";
                render_table_rows(rows, parseInt(req_per_page), parseInt(element.text));
                if (prev_link.getAttribute("onclick") === "return false") {
                    prev_link.setAttribute("onclick", `active_page('prev',\"${rows}\",${req_per_page})`);
                }
                if (next_link.getAttribute("onclick") === "return false") {
                    next_link.setAttribute("onclick", `active_page('next',\"${rows}\",${req_per_page})`);
                }
            }
        }

        // Render the table's row in table request-table
        function render_table_rows(rows, req_per_page, page_no) {
            const response = JSON.parse(window.atob(rows));
            const resp = response.slice(req_per_page * (page_no - 1), req_per_page * page_no)
            $('#request-table').empty()
            $('#request-table').append('<tr><th>Index</th><th>Request No</th><th>Title</th></tr>');
            resp.forEach(function (element, index) {
                if (Object.keys(element).length > 0) {
                    const { req_no, title } = element;
                    const td = `<tr><td>${++index}</td><td>${req_no}</td><td>${title}</td></tr>`;
                    $('#request-table').append(td)
                }
            });
        }

        // Pagination logic implementation
        function pagination(data, myarr) {
            const all_data = window.btoa(JSON.stringify(myarr));
            $(".pagination").empty();
            if (data.req_per_page !== 'ALL') {
                let pager = `<a href="#" id="prev_link" onclick=active_page('prev',\"${all_data}\",${data.req_per_page})>&laquo;</a>` +
                    `<a href="#" class="active" onclick=active_page(this,\"${all_data}\",${data.req_per_page})>1</a>`;
                const total_page = Math.ceil(parseInt(myarr.length) / parseInt(data.req_per_page));
                if (total_page < pagination_visible_pages) {
                    render_table_rows(all_data, data.req_per_page, data.page_no);
                    for (let num = 2; num <= total_page; num++) {
                        pager += `<a href="#" onclick=active_page(this,\"${all_data}\",${data.req_per_page})>${num}</a>`;
                    }
                } else {
                    render_table_rows(all_data, data.req_per_page, data.page_no);
                    for (let num = 2; num <= pagination_visible_pages; num++) {
                        pager += `<a href="#" onclick=active_page(this,\"${all_data}\",${data.req_per_page})>${num}</a>`;
                    }
                    for (let num = pagination_visible_pages + 1; num <= total_page; num++) {
                        pager += `<a href="#" style="display:none;" onclick=active_page(this,\"${all_data}\",${data.req_per_page})>${num}</a>`;
                    }
                }
                pager += `<a href="#" id="next_link" onclick=active_page('next',\"${all_data}\",${data.req_per_page})>&raquo;</a>`;
                $(".pagination").append(pager);
            } else {
                render_table_rows(all_data, myarr.length, 1);
            }
        }

        //calling pagination function
        pagination(data, myarr);


        // trigger when requests per page dropdown changes
        function filter_requests() {
            const data = { "req_per_page": document.getElementById("req_per_page").value, "page_no": 1 };
            pagination(data, myarr);
        }

.box {
	float: left;
	padding: 50px 0px;
}

.clearfix::after {
	clear: both;
	display: table;
}

.options {
	margin: 5px 0px 0px 0px;
	float: left;
}

.pagination {
	float: right;
}

.pagination a {
	color: black;
	float: left;
	padding: 8px 16px;
	text-decoration: none;
	transition: background-color .3s;
	border: 1px solid #ddd;
	margin: 0 4px;
}

.pagination a.active {
	background-color: #4CAF50;
	color: white;
	border: 1px solid #4CAF50;
}

.pagination a:hover:not(.active) {
	background-color: #ddd;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div>
    <table id="request-table">
   </table>
</div>

<div class="clearfix">
	<div class="box options">
		<label>Requests Per Page: </label>
      <select id="req_per_page" onchange="filter_requests()">
			<option>5</option>
			<option>10</option>
			<option>ALL</option>
		</select>
	</div>
	<div class="box pagination">
	</div>
</div>

Simple pagination in javascript

Tags:

Javascript

Pagination

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