diff --git a/src/to-json/src/convert.rs b/src/to-json/src/convert.rs
new file mode 100644
index 0000000..55f9e91
--- /dev/null
+++ b/src/to-json/src/convert.rs
@@ -0,0 +1,21 @@
+use serde_json as json;
+use crate::parser::{parser, Value};
+
+fn json_convert(content: &str) -> Result<String, String> { // convert to JSON format
+    let data = match parser(content)? {
+        Value::JSON(_json) => json::to_string(&_json),
+        Value::YAML(_yaml) => json::to_string(&_yaml),
+        Value::TOML(_toml) => json::to_string(&_toml),
+    };
+    match data {
+        Ok(data) => Ok(data),
+        Err(err) => Err(err.to_string()),
+    }
+}
+
+pub fn to_json(content: &str) -> Option<String> { // to JSON string
+    match json_convert(content) {
+        Ok(data) => Some(data),
+        Err(_) => None,
+    }
+}
diff --git a/src/to-json/src/lib.rs b/src/to-json/src/lib.rs
index 4f1b9a0..ce4d1e6 100644
--- a/src/to-json/src/lib.rs
+++ b/src/to-json/src/lib.rs
@@ -1,2 +1,4 @@
 mod ffi;
 mod json;
+mod parser;
+mod convert;