ass_to_vtt.js

'use strict';

var fs 			= require('fs'),
	readline 	= require('readline');

var ass_to_vtt = (file_in, file_out, cb)=>{
	var order = [],
	gotOrder = false;
	fs.writeFileSync(file_out, 'WEBVTT\n\n');
	readline.createInterface({
  		input: fs.createReadStream(file_in)
  	}).on('line', (line)=>{
  		if(/Format: /.test(line)){
  			order = line.split('Format: ')[1].split(', ');
  			if(order.indexOf('Text') !== -1)
	  			gotOrder = true;
  		}else if(gotOrder && /Dialogue: /.test(line)){
  			var explode = line.split('Dialogue: ')[1].split(',');
	  		if(explode.length == order.length){
		  		var	start = '0' + explode[order.indexOf('Start')],
		  		end = '0' + explode[order.indexOf('End')],
		  		txt = explode[order.indexOf('Text')],
		  		vtt = (start + ' --> ' + end + '\n' + txt + '\n\n');
				fs.appendFileSync(file_out, vtt);
			}
		}
	}).on('close', ()=>{
		cb(true);
	});
};

ass_to_vtt('English.ass', 'English.vtt', ()=>{
	console.log('done');
});

Node js function

translate a ass subtitles to vtt subs. nice for html5.