Style ignored on empty cells

[azukaar]

In the XLSX files, the empty cells are skipped, but they are skipped even if they hold style informations.
I think they shouldn't be skipped in this case as they still hold relevant information, plus, importing + exporting an excel file without changing it should be an idempotent operation.

See : #8

The changes you proposed in the pull request #7 are made to the source files under bits and compiled. There is a new test in tests\test-styles.js that verifies styles in blank cells persist round trip. Changes are merged into the beta branch (https://github.com/protobi/js-xlsx#beta), tagged as version 0.8.6 and published to npm and bower.

describe('styles with blank cells', function () {
  it ('retains styles with blank cells', function() {


    var OUTFILE = '/tmp/ex1.xlsx';
    var OUTFILE2 = '/tmp/ex1a.xlsx';

    var workbook = {
      SheetNames : ["Sheet1"],
      Sheets: {
        "Sheet1": {
          "B2": {v: "Top left", s: { border: { top: { style: 'medium', color: { rgb: "FFFFAA00"}}, left: { style: 'medium', color: { rgb: "FFFFAA00"}} }}},
          "C2": {v: "Top right", s: { border: { top: { style: 'medium', color: { rgb: "FFFFAA00"}}, right: { style: 'medium', color: { rgb: "FFFFAA00"}} }}},
          "B3": {v: "Bottom left", s: { border: { bottom: { style: 'medium', color: { rgb: "FFFFAA00"}}, left: { style: 'medium', color: { rgb: "FFFFAA00"}} }}},
          "C3": {v: "", s: { border: { bottom: { style: 'medium', color: { rgb: "FFFFAA00"}}, right: { style: 'medium', color: { rgb: "FFFFAA00"}} }}},
          "!ref":"B2:C3"
        }
      }
    };

    // write the file and read it back...
    XLSX.writeFile(workbook, OUTFILE, {bookType: 'xlsx', bookSST: false});
    var workbook2 = XLSX.readFile(OUTFILE, {cellStyles: true});
    assert(basicallyEquals(workbook.Sheets, workbook2.Sheets));

    XLSX.writeFile(workbook2, OUTFILE2, {bookType: 'xlsx', bookSST: false});
    var workbook3 = XLSX.readFile(OUTFILE2, {cellStyles: true});
    assert(basicallyEquals(workbook.Sheets, workbook3.Sheets))
  });
});

[azukaar]

Nice, perfect