pagination-fns.js

pagination-fns.js

function offset(page, itemsPerPage){  
  return (page - 1) * itemsPerPage;
}

function maxPages(perPage, totalItems){
  return Math.ceil(totalItems / perPage);
}

function isValidPage(page, itemsPerPage, totalItems){
  return ((page > 0) && (page <= maxPages(itemsPerPage, totalItems)));
}

function pageBack(page){
  if(page > 1){
    return page - 1;
  }
}

function pageForward(page, perPage, totalItems){
  var next = page + 1;
  if(next <= maxPages(perPage, totalItems)){
    return next;
  }
}


function pageNums(page, perPage, totalItems){
  if( isValidPage(page, perPage, totalItems) ){
    var N = maxPages(perPage, totalItems);
    return Array.apply(null, {length: N}).map(Number.call, Number).map(
      function(i){
        return i + page;
      }
    );
  }
}