DNA to RNA scrap

gistfile1.js

(function codon(sequence){
  var sequence = sequence.toUpperCase().split('');
	var codons = "";
	sequence.forEach(function(ch, i){
		if (i != 0 && i % 3 === 0) {
			returned += " ";
		}
		switch (ch) {
			case 'G':
				returned += 'C'
				break;
			case 'T':
				returned += 'A'
				break;
			case 'A':
				returned += 'U'
				break;
			case 'C':
				returned += 'G'
				break;
		}
	});
	returned = returned.split(' ');
	returned.forEach(function(codon, i){
		switch(codon) {
			case 'UUU':
				return
		//UNFINISHED
		}
	});
	return returned;
})('GTCTACAAACAATGCGCCTAGGGTATGGCCCACACCTCACCACTGATTGATCTA');