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export-to-excel-service.js
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export-to-excel-service.js
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/**
* DataFormsJS <export-to-excel-service> Web Component
*
* This service allows a user to export an HTML <table> to an Excel file download
* based on the attributes:
* data-export-excel-selector
* data-export-file-name
* data-worksheet-name
* data-export-all
*
* [data-export-excel-selector] is required with a valid selector to a <table>
* while [data-export-file-name] and [data-worksheet-name] are optional defaulting
* to "Report.xlsx" and "Report" respectively. By default only visible records are
* exported unless the attribute [data-export-all] is defined.
*
* Exports happen directly in the browser through JavaScript and no server-side calls
* are made which makes the export/download appear almost instantly to the user.
*
* The script uses the external library ExcelJS and the first time the user exports an
* Excel file this service will download ExcelJS from a CDN. The generated Excel file
* contains a fixed header row using a gray and bold style and a filter set. The width
* of columns is based on the data. ExcelJS has many formatting options so if you need
* something similar or a custom version of this script then this file provides a good
* starting point for custom Excel Development.
*
* The DataFormsJS Framework has a corresponding plugin: [js/plugins/exportToExcel.js].
*
* Example:
* <export-to-excel-service></export-to-excel-service>
* <button data-export-csv-selector="table"
* data-export-file-name="Report.xlsx"
* data-worksheet-name="Report">Export to Excel</button>
*
* @see https://github.com/exceljs/exceljs/
*/
/* Validates with both [eslint] and [jshint] */
/* global ExcelJS */
/* eslint-env browser */
/* eslint quotes: ["error", "single", { "avoidEscape": true }] */
/* eslint strict: ["error", "function"] */
/* eslint spaced-comment: ["error", "always"] */
/* eslint no-console: ["error", { allow: ["log", "warn", "error"] }] */
/* jshint esversion:8, laxbreak:true */
import { WebComponentService } from './WebComponentService.js';
import { showErrorAlert } from './utils.js';
/**
* Check if text is a number (excluding zero padding numbers).
* Zero-padded numbers - example "000123" need to be kept in string format
* for Excel otherwise data will be lost if a user is expecting zero-padding
* numbers (happens often with legacy databases).
*
* @param {string} value
* @returns {boolean}
*/
function isNumeric(value) {
return (
!isNaN(value)
&& isFinite(value)
&& !(value.length > 1 && value.substring(0, 1) === '0')
);
}
/**
* Convert to correct type from string (example '123' string to 123 number).
* This is based on what is needed for ExcelJS.
*
* @param {string} value
* @returns
*/
function excelValue(value) {
value = value.trim();
if (value === '') {
return null;
} else if (isNumeric(value)) {
return parseFloat(value);
} else {
// This code handles some known edge cases such as the following value
// will be parsed as year 123 and an unknown timezone so the browser
// defaults it to the user's timezone:
// `new Date('123 (TEST)')`
// If this happens Excel will shows a "#####" error due to negative
// date when using Excel's 1900 date system.
const dateValue = new Date(value);
if (!isNaN(dateValue.getTime()) && dateValue.getYear() > 0
&& (value.includes('-') || value.includes(',') || value.includes('/'))
) {
return dateValue;
}
}
return value;
}
function downloadExcelJS(callback) {
if (window.ExcelJS !== undefined) {
callback();
return;
}
const script = document.createElement('script');
script.src = 'https://cdn.jsdelivr.net/npm/exceljs@4.3.0/dist/exceljs.min.js';
script.onload = callback;
document.querySelector('head').appendChild(script);
}
/**
* Return true if a file name has invalid characters.
* Based on `InvalidFileNameChars` from:
* https://github.com/microsoft/referencesource/blob/master/mscorlib/system/io/path.cs
*
* @param {string} fileName
* @returns {boolean}
*/
function hasInvalidFileNameChars(fileName) {
const invalidChars = ['"', '<', '>', '|', ':', '*', '?', '\\', '/'];
for (const char of invalidChars) {
if (fileName.includes(char)) {
return true;
}
}
for (let ascii = 0; ascii < 32; ascii++) {
if (fileName.includes(String.fromCharCode(ascii))) {
return true;
}
}
return false;
}
function exportTable(event) {
// Use an HTML attribute to track if file is being generated and if the
// user clicks while the previous export is still running then exit.
// ExcelJS is over 250 kB in gzip size so if a user is on a slow connection
// or device it can take time the first time this function runs.
const attrRunning = 'data-running-export';
if (event.target.getAttribute(attrRunning) !== null) {
return;
}
event.target.setAttribute(attrRunning, '');
if (event.target.nodeName === 'BUTTON') {
event.target.disabled = true;
}
downloadExcelJS(() => {
// Get export settings
const selector = event.target.getAttribute('data-export-excel-selector');
let exportFileName = event.target.getAttribute('data-export-file-name');
if (exportFileName
&& (
exportFileName.length <= 5
|| !exportFileName.endsWith('.xlsx')
|| hasInvalidFileNameChars(exportFileName)
)
) {
showErrorAlert('Attribute [data-export-file-name] must be a valid name with file type [*.xlsx]');
return;
}
exportFileName = exportFileName || 'Report.xlsx';
let worksheetName = event.target.getAttribute('data-worksheet-name');
worksheetName = worksheetName || exportFileName.substring(0, exportFileName.length - 5);
if (worksheetName.length > 31) {
worksheetName = worksheetName.substring(0, 31);
}
const exportAll = (event.target.getAttribute('data-export-all') !== null);
// Get Table Header
const table = document.querySelector(selector);
const rows = [];
const colWidths = [];
let row = [];
let rowEl = table.tHead.rows[0];
for (let n = 0, m = rowEl.cells.length; n < m; n++) {
const text = rowEl.cells[n].textContent;
row.push(text);
// Add extra padding/space for bold font - larger of (1.2x or 4 extra)
const len = text.trim().length;
const width = parseInt(Math.max(len * 1.2, len + 4));
colWidths.push(width);
}
rows.push(row);
// Get Table Rows
const tableRows = table.tBodies[0].rows;
for (let x = 0, y = tableRows.length; x < y; x++) {
rowEl = tableRows[x];
if (!exportAll && rowEl.style.display === 'none') {
// Exclude hidden rows
continue;
}
row = [];
for (let n = 0, m = rowEl.cells.length; n < m; n++) {
const cell = rowEl.cells[n];
let value = cell.getAttribute('data-value');
if (value === null) {
value = cell.textContent;
}
let width = value.trim().length;
value = excelValue(value);
if (value instanceof Date) {
width = 12;
} else if (typeof value === 'number') {
width = value.toString().length + 2;
} else if (width <= 20) {
width += 2;
}
colWidths[n] = Math.max(colWidths[n], width);
row.push(value);
}
rows.push(row);
}
// Build Workbook and add data
const workbook = new ExcelJS.Workbook();
const worksheet = workbook.addWorksheet(worksheetName);
for (const row of rows) {
worksheet.addRow(row);
}
// Font Style for Header Row
const firstRow = worksheet.getRow(1);
for (let n = 0; n < colWidths.length; n++) {
const cell = firstRow.getCell(n+1);
cell.fill = {
type: 'pattern',
pattern: 'solid',
fgColor: { argb: 'FFF2F2F2' },
};
cell.font = { bold: true };
}
// Set column width based on size of data but limit to a max of 50
// otherwise large columns take up the width of the screen and can
// be hard (or a hassle) for users to reduce the size of the column.
for (let n = 0; n < colWidths.length; n++) {
worksheet.getColumn(n + 1).width = Math.min(50, colWidths[n]);
}
// Setup filter
worksheet.autoFilter = {
from: {
row: 1,
column: 1
},
to: {
row: rows.length,
column: colWidths.length
}
};
// Freeze Header Row
worksheet.views = [
{ state: 'frozen', ySplit: 1 }
];
// Save (appears as file download to user)
workbook.xlsx.writeBuffer().then(data => {
const mimeType = 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet';
const blob = new Blob([data], { type: mimeType });
if (navigator.msSaveBlob !== undefined) {
navigator.msSaveBlob(blob, exportFileName);
} else {
const link = document.createElement('a');
const url = URL.createObjectURL(blob);
link.setAttribute('href', url);
link.setAttribute('download', exportFileName);
link.style.visibility = 'hidden';
document.body.appendChild(link);
link.click();
document.body.removeChild(link);
}
// Enable original Export Link/Button
event.target.removeAttribute(attrRunning);
if (event.target.nodeName === 'BUTTON') {
event.target.disabled = false;
}
});
});
}
window.customElements.define('export-to-excel-service', class ExportToExcelService extends WebComponentService {
onLoad() {
// Find Elements
const actionElements = document.querySelectorAll('[data-export-excel-selector]');
// Check browser support
let isSupported = false;
if (actionElements.length > 0) {
let firstLinkFound = document.querySelector('a');
if (firstLinkFound === null) {
firstLinkFound = document.createElement('a');
}
isSupported = (navigator.msSaveBlob !== undefined || firstLinkFound.download !== undefined);
}
// Update the Elements
for (const element of actionElements) {
// If supported then setup and if not supported then hide the button
// (Example, this doesn't work on older iPhones).
if (isSupported) {
element.addEventListener('click', exportTable);
} else {
element.style.display = 'none';
}
}
}
});