중복 가입 방지 구현

@@ -36,7 +36,6 @@ const SigninPage = (props) => {
                 cookie.save('username', response.username, {
                     expires
                 })
-                alert('Login success');
                 props.history.push('/mypick');
             } else if(response.message === "user does not exist"){
                 alert('User does not exist');

@@ -37,12 +37,18 @@ const SigninPage = (props) => {
             fetch("http://localhost:3000/api/signup", signup_info)
             .then(response => response.json())
             .then(json => {
-                if(json.code === 200) {
+                if(json.message === 'success') {
                     alert('회원가입에 성공했습니다.');
                     props.history.push('/signin');
-                }
-                else if(json.code === 400) {
+                } 
+                else if(json.message === 'user exist') {
+                    alert('이미 존재하는 유저입니다');
+                    setUsername('');
+                    setPassword('');
+                } else {
                     alert('회원가입에 실패했습니다.');
+                    setUsername('');
+                    setPassword('');
                 }
             })
         }

@@ -40,28 +40,40 @@ app.get("/api/datas", (req, res) => {
   res.send(iconv.decode(dataBuffer, "EUC-KR").toString());
 });
 
-// ???? ???? ??
 // signup
 app.post("/api/signup", (req, res) => {
-  let sql = "INSERT INTO USER (name, pw) VALUES(?, ?)";
-  let plainPassword = req.body.password;
-  bcrypt.hash(plainPassword, saltRounds, function (err, hash) {
-    const params = [req.body.username, hash];
-    connection.query(sql, params, (err, rows, fields) => {
-      if (err) {
-        console.log(err);
-        res.send({
-          code: 400,
-          message: "error",
-        });
-      } else {
-        res.send({
-          code: 200,
-          message: "success",
+
+  let sql_usercheck = `SELECT * FROM USER WHERE name='${req.body.username}';`;
+  connection.query(sql_usercheck, (err, rows, fields) => {
+    console.log(rows);
+    if(rows.length!==0) {
+      return res.json({
+        code: 400,
+        message: 'user exist'
+      })
+    }
+    else {
+      let sql = "INSERT INTO USER (name, pw) VALUES(?, ?)";
+      let plainPassword = req.body.password;
+      bcrypt.hash(plainPassword, saltRounds, function (err, hash) {
+        const params = [req.body.username, hash];
+        connection.query(sql, params, (err, rows, fields) => {
+          if (err) {
+            console.log(err);
+            res.send({
+              code: 400,
+              message: "error",
+            });
+          } else {
+            res.send({
+              code: 200,
+              message: "success",
+            });
+          }
         });
-      }
-    });
-  });
+      });
+    }
+  })
 });
 
 app.post("/api/signin", (req, res) => {