I have a sample array as follows
var arr = [ [ 1373628934214, 3 ], [ 1373628934218, 3 ], [ 1373628934220, 1 ], [ 1373628934230, 1 ], [ 1373628934234,
Remember you can access good old ECMAScript APIs, in this case, JSON.stringify().
JSON.stringify()
For simple arrays like the one in your example:
require('fs').writeFile( './my.json', JSON.stringify(myArray), function (err) { if (err) { console.error('Crap happens'); } } );