node-espeak

This simply uses the eSpeak cli program to
generate wav audio data from text strings. You can then use the raw binary data
to output to a file, send as a http download, get as a base64-encoded data URI
string, or whatever else.
Install
$ npm install espeak
Usage
var espeak = require('espeak');
espeak.speak('hello world', function(err, wav) {
if (err) return console.error(err);
var buffer = wav.buffer;
var dataUri = wav.toDataUri();
});
espeak.speak('hello world, slower', ['-p 60', '-s 90', '-g 30'], function(err, wav) {});
Related Modules
There are some related modules, although there seems to be some scattered
forks and it wasn't clear to the author which was updated and/or compatible with
Node.js/npm at the time of writing this.