Discussion on: Daily Challenge #175 - Complementary DNA

function DNA_strand (str) {
    let result = '';
    for(i=0; i<str.length; i++){    
        switch (str[i]) {
            case 'A':
                result = result + 'T';
                break;
            case 'T':
                result = result + 'A';
                break;
            case 'C':
                result = result + 'G';
                break;
            case 'G':
                result = result + 'C';
                break;
            default:
                return 'Your DNA is not from this planet';
        }
    }
    return result
};
```