subject = 'a " b \\" c \\\\" d "\\\\" e " f';
print(subject);
result = subject.replace(/([^"\\]*(?:\\.[^"\\]*)*)"/g, '$1\\"');
print(result);
c3ViamVjdCA9ICdhICIgYiBcXCIgYyBcXFxcIiBkICJcXFxcIiBlICIgZic7CnByaW50KHN1YmplY3QpOwpyZXN1bHQgPSBzdWJqZWN0LnJlcGxhY2UoLyhbXiJcXF0qKD86XFwuW14iXFxdKikqKSIvZywgJyQxXFwiJyk7CnByaW50KHJlc3VsdCk7Cg==