Add lastColumn property (fixes #1453)

lib/doc/worksheet.js

@@ -260,6 +260,10 @@ class Worksheet {
     this.workbook.definedNames.spliceColumns(this.name, start, count, inserts.length);
   }
 
+  get lastColumn() {
+    return this.getColumn(this.columnCount);
+  }
+
   get columnCount() {
     let maxCount = 0;
     this.eachRow(row => {

spec/integration/gold.spec.js

@@ -31,6 +31,9 @@ describe('Gold Book', () => {
         hyperlink: 'https://www.npmjs.com/package/exceljs',
         text: 'exceljs',
       });
+
+      expect(ws.lastColumn).to.equal(ws.getColumn(2));
+      expect(ws.lastRow).to.equal(ws.getRow(6));
     });
 
     it('Styles', () => {});

spec/integration/pr/test-pr-1487.spec.js

@@ -0,0 +1,14 @@
+const ExcelJS = verquire('exceljs');
+
+describe('github issues', () => {
+  describe('pull request 1487 - lastColumn with an empty column', () => {
+    it('Reading 1904.xlsx', () => {
+      const wb = new ExcelJS.Workbook();
+      return wb.xlsx.readFile('./spec/integration/data/1904.xlsx').then(() => {
+        const ws = wb.getWorksheet('Sheet1');
+        expect(ws.lastColumn).to.equal(ws.getColumn(2));
+      });
+    });
+  });
+  // the new property is also tested in gold.spec.js
+});