js pagination function with bootstrap

function pagination(total, pageset, blockset, page) {
    var total = total ? total : 0;
    var pageset = pageset ? pageset : 10;
    var blockset = blockset ? blockset : 10;
    var page = page ? page : 1;

    var totalpage = Math.ceil (total / pageset); // total pages
    var totalblock = Math.ceil (totalpage / blockset); // total page blocks
    var block = Math.ceil (page / blockset); // current block
    var first_page = ((block - 1) * blockset) + 1; // first page of current block
    var last_page = Math.min (totalpage, block * blockset); // last page of current block
    var prev_page = page - 1; // previous page
    var next_page = page + 1; // next page
    var prev_block = block - 1; // previous block
    var next_block = block + 1; // next block
    var prev_block_page = prev_block * blockset; // last page of previous block
    var next_block_page = next_block * blockset - (blockset - 1); // first page of next block

    var paginationblock = "<div aria-label='...'><ul class='pagination justify-content-center'>";

    if( page > 1 ) paginationblock += "<li class='page-item'><a class='page-link' href='1'>1</a></li>";
    else paginationblock +=  "<li class='page-item disabled'><a class='page-link' href='1' tabindex='-1' aria-disabled='true'>1</a></li>";

    if( prev_block > 0 ) paginationblock += "<li class='page-item'><a class='page-link' href='" + prev_block_page + "'><i class='fas fa-chevron-left'></i></a></li>";
    else paginationblock += "<li class='page-item disabled'><a class='page-link' href='#!' tabindex='-1' aria-disabled='true'><i class='fas fa-chevron-left'></i></a></li>";

    for ( var i=first_page; i <= last_page; i++ ) {
        if(i != page) paginationblock +=  "<li class='page-item'><a class='page-link' href='" + i + "'>" + i + "</a></li>";
        else paginationblock +=  "<li class='page-item active' aria-current='page'><a class='page-link' href='#!'>" + i + "</a></li>";
    }

    if( next_block <= totalblock ) paginationblock += "<li class='page-item'><a class='page-link' href='" + next_block_page + "'><i class='fas fa-chevron-right'></i></a></li>";
    else paginationblock +=  "<li class='page-item disabled'><a class='page-link' href='#!' tabindex='-1' aria-disabled='true'><i class='fas fa-chevron-right'></i></a></li>";

    if( page < totalpage ) paginationblock += "<li class='page-item'><a class='page-link' href='" + totalpage + "'>" + totalpage + "</a></li>";
    else paginationblock +=  "<li class='page-item disabled'><a class='page-link' href='#!' tabindex='-1' aria-disabled='true'>" + totalpage + "</a></li>";

    paginationblock += "</ul></div>";

    return paginationblock;
}