publisher.js

displayPublisherData();
function displayPublisherData() {
 let arr = localStorage.getItem('bookData');
 if (arr == null) {
 data = [];
 } else {
 data = JSON.parse(arr);
 }
 let rows = '';
 const arr1 = getUniqueListBy(data, 'publisher');
 arr1.forEach((item, index) => {
 rows += `<tr class = 'tr'>
 <td>${index + 1}</td>
 <td>${item.publisher}</td>
 <td>${bookNames(item['publisher'])}</td>
 <td><button onClick = 'deleteData(${index})'>Delete</button></td>
 </tr>`
 })
 var tbody = document.getElementById("publisherTable");
 tbody.innerHTML = rows;
}
function getUniqueListBy(arr, key) {
 return [...new Map(arr.map(item => [item[key], item])).values()]
}
function bookNames(publisher) {
 const counts = data.filter(item => item['publisher'] === publisher).map(i =>
i.name);
return counts.length;
}
function deleteData(a) {
 const arr = getUniqueListBy(data, 'publisher');
 let author = arr[a]['publisher'];
 const dele = data.filter(data => data.publisher !== author);
 localStorage.setItem('bookData', JSON.stringify(dele));
 displayPublisherData();
}