var a = `
#EXTM3U
#EXT-X-STREAM-INF:RESOLUTION=640x272,BANDWIDTH=372000
http://myhost.com/source1.m3u8
#EXT-X-STREAM-INF:RESOLUTION=1128x480,BANDWIDTH=566000
http://myhost.com/source2.m3u8
#EXT-X-STREAM-INF:RESOLUTION=1280x544,BANDWIDTH=1034000
http://myhost.com/source3.m3u8
`
a = a.split(/^(^#)+$/gm);
console.log(a);
// отдает всю строку в нулевом ключе
console.log(
a
.split(/\r?\n/)
.filter(function(line) {
return line.match(/^[^#]/);
})
);