How can you read excel 2007 file (xlsx) using javascript/VBScript

I've done some very simple xlsx parsing in the browser. See https://gist.github.com/3375836. Try it out at http://jsfiddle.net/fAKGA/2. Copied here for convenience:

/*
    Relies on jQuery, underscore.js, Async.js (https://github.com/caolan/async), and zip.js (http://gildas-lormeau.github.com/zip.js).
    Tested only in Chrome on OS X.

    Call xlsxParser.parse(file) where file is an instance of File. For example (untested):

    document.ondrop = function(e) {
        var file = e.dataTransfer.files[0];
        excelParser.parse(file).then(function(data) {
            console.log(data);
        }, function(err) {
            console.log('error', err);
        });
    }
*/

xlsxParser = (function() {
    function extractFiles(file) {
        var deferred = $.Deferred();

        zip.createReader(new zip.BlobReader(file), function(reader) {
            reader.getEntries(function(entries) {
                async.reduce(entries, {}, function(memo, entry, done) {
                    var files = ['xl/worksheets/sheet1.xml', 'xl/sharedStrings.xml'];
                    if (files.indexOf(entry.filename) == -1) return done(null, memo);

                    entry.getData(new zip.TextWriter(), function(data) {
                        memo[entry.filename.split('/').pop()] = data;
                        done(null, memo);
                    });
                }, function(err, files) {
                    if (err) deferred.reject(err);
                    else deferred.resolve(files);
                });
            });
        }, function(error) { deferred.reject(error); });

        return deferred.promise();
    }

    function extractData(files) {
        var sheet = $(files['sheet1.xml']),
            strings = $(files['sharedStrings.xml']),
            data = [];

        var colToInt = function(col) {
            var letters = ["", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"];
            var col = $.trim(col).split('');

            var n = 0;

            for (var i = 0; i < col.length; i++) {
                n *= 26;
                n += letters.indexOf(col[i]);
            }

            return n;
        };

        var Cell = function(cell) {
            cell = cell.split(/([0-9]+)/);
            this.row = parseInt(cell[1]);
            this.column = colToInt(cell[0]);
        };

        var d = sheet.find('dimension').attr('ref').split(':');
        d = _.map(d, function(v) { return new Cell(v); });

        var cols = d[1].column - d[0].column + 1,
            rows = d[1].row - d[0].row + 1;

        _(rows).times(function() {
            var _row = [];
            _(cols).times(function() { _row.push(''); });
            data.push(_row);
        });

        sheet.find('sheetData row c').each(function(i, c) {
            var $cell = $(c),
                cell = new Cell($cell.attr('r')),
                type = $cell.attr('t'),
                value = $cell.find('v').text();

            if (type == 's') value = strings.find('si t').eq(parseInt(value)).text();

            data[cell.row - d[0].row][cell.column - d[0].column] = value;
        });

        return data;
    }

    return {
        parse: function(file) {
            return extractFiles(file).pipe(function(files) {
                return extractData(files);
            });
        }
    }
})();

In short, No. The is no way for javascript to access the filesystem, this would be a major security threat/attack vector.

Absolutely not. For security purposes, this must be done server side. I can't think of single reason you wouldn't want to do it that way anyway.