Using Javascript to convert .srt to .webvtt

Question

Looking for a client-side way to convert .srt to .WebVtt, as HTML5 video doesn't support .srt for <track> tags. So far I only came across server-side solutions. Thanks ahead

Answer 1

From https://github.com/silviapfeiffer/silviapfeiffer.github.io/blob/master/index.html

function convert() {
      var input = document.getElementById("srt");
      var output = document.getElementById("webvtt");
      var srt = input.value;
      var webvtt = srt2webvtt(srt);
      output.innerHTML = "<textarea rows=20 cols=80>"
                         + webvtt +
                         "</textarea>";
    }
    function srt2webvtt(data) {
      // remove dos newlines
      var srt = data.replace(/\r+/g, '');
      // trim white space start and end
      srt = srt.replace(/^\s+|\s+$/g, '');
      // get cues
      var cuelist = srt.split('\n\n');
      var result = "";
      if (cuelist.length > 0) {
        result += "WEBVTT\n\n";
        for (var i = 0; i < cuelist.length; i=i+1) {
          result += convertSrtCue(cuelist[i]);
        }
      }
      return result;
    }
    function convertSrtCue(caption) {
      // remove all html tags for security reasons
      //srt = srt.replace(/<[a-zA-Z\/][^>]*>/g, '');
      var cue = "";
      var s = caption.split(/\n/);
      // concatenate muilt-line string separated in array into one
      while (s.length > 3) {
          for (var i = 3; i < s.length; i++) {
              s[2] += "\n" + s[i]
          }
          s.splice(3, s.length - 3);
      }
      var line = 0;
      // detect identifier
      if (!s[0].match(/\d+:\d+:\d+/) && s[1].match(/\d+:\d+:\d+/)) {
        cue += s[0].match(/\w+/) + "\n";
        line += 1;
      }
      // get time strings
      if (s[line].match(/\d+:\d+:\d+/)) {
        // convert time string
        var m = s[1].match(/(\d+):(\d+):(\d+)(?:,(\d+))?\s*--?>\s*(\d+):(\d+):(\d+)(?:,(\d+))?/);
        if (m) {
          cue += m[1]+":"+m[2]+":"+m[3]+"."+m[4]+" --> "
                +m[5]+":"+m[6]+":"+m[7]+"."+m[8]+"\n";
          line += 1;
        } else {
          // Unrecognized timestring
          return "";
        }
      } else {
        // file format error or comment lines
        return "";
      }
      // get cue text
      if (s[line]) {
        cue += s[line] + "\n\n";
      }
      return cue;
    }