npm install json2xls

var json2xls = require('json2xls');
var json = {
    foo: 'bar',
    qux: 'moo',
    poo: 123,
    stux: new Date()
}

var xls = json2xls(json);

fs.writeFileSync('data.xlsx', xls, 'binary');

var jsonArr = [{
    foo: 'bar',
    qux: 'moo',
    poo: 123,
    stux: new Date()
},
{
    foo: 'bar',
    qux: 'moo',
    poo: 345,
    stux: new Date()
}];

app.use(json2xls.middleware);

app.get('/',function(req, res) {
    res.xls('data.xlsx', jsonArr);
});

var xls = json2xls(json, options);
res.xls('data.xlsx', jsonArr, options);

- style: a styles xml file, see <https://github.com/functionscope/Node-Excel-Export>
- fields: either an array or map containing field configuration:
    - array: a list of names of fields to be exported, in that order
    - object: a map of names of fields to be exported and the types of those fields. Supported types are 'number','string','bool'

var json2xls = require('json2xls');
var json = {
    foo: 'bar',
    qux: 'moo',
    poo: 123,
    stux: new Date()
}

//export only the field 'poo'
var xls = json2xls(json,{
    fields: ['poo']
});

//export only the field 'poo' as string
var xls = json2xls(json,{
    fields: {poo:'string'}
});

fs.writeFileSync('data.xlsx', xls, 'binary');