diff --git a/.vscode/launch.json b/.vscode/launch.json
index 533d50e..3e473f3 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -15,6 +15,15 @@
       "outFiles": [
         "${workspaceFolder}/**/*.js"
       ]
+    },
+    {
+      "type": "node",
+      "request": "launch",
+      "name": "run js source code",
+      "skipFiles": [
+        "<node_internals>/**"
+      ],
+      "program": "${workspaceFolder}/src/index.js",
     }
   ]
 }
\ No newline at end of file
diff --git a/src/index.js b/src/index.js
new file mode 100644
index 0000000..41ad38f
--- /dev/null
+++ b/src/index.js
@@ -0,0 +1,203 @@
+const code = `<div class="test"><span>abc</span></div>`;
+
+/**
+ * syntax
+ *   html       = '<' identifier props '>' html '</' identifier '>'
+ *   props      = '' | identifier '=' '"' identifier '"' props
+ * 
+ *   identifier = [a-z]+
+ *   whitespace = ' ' | '\n'
+ * 
+ * example
+ *   <div class="test"><span>abc</span></div>
+ */
+
+const parser = code => {
+  let pos;
+  let end;
+  let token;
+  let tokenKind = {
+    leftBracket: '<',
+    rightBracket: '>',
+    leftBracketSlash: '</',
+    identifier: '(identifier)',
+    equal: '=',
+    quote: '"',
+    eof: '(eof)',
+  };
+
+  const parse = () => {
+    pos = 0;
+    end = code.length;
+
+    nextToken();  // <
+    assert(tokenKind.leftBracket);
+
+    const html = parseHtml();
+
+    nextToken();  // eof
+    assert(tokenKind.eof);
+
+    return html;
+  };
+
+  const parseHtml = () => {
+    nextToken();  // identifier
+    assert(tokenKind.identifier);
+    const tagName = token;
+
+    // props
+    nextToken();  // identifier | >
+    let props;
+    if (token.kind === tokenKind.rightBracket) {  // >
+      props = [];
+    } else {
+      assert(tokenKind.identifier);
+      props = parseProps();  // identifier
+      assert(tokenKind.rightBracket);  // >
+    }
+
+    // child
+    nextToken();  // identifier | <
+    let child;
+    if (token.kind === tokenKind.identifier) {  // identifier
+      child = token;
+    } else {  // <
+      assert(tokenKind.leftBracket);
+      child = parseHtml();
+      assert(tokenKind.rightBracket);  // >
+    }
+
+    nextToken();  // </
+    assert(tokenKind.leftBracketSlash);
+
+    nextToken();  // identifier
+    assert(tokenKind.identifier);
+    const rightTagName = token;
+
+    nextToken();  // >
+    assert(tokenKind.rightBracket);
+
+    return {
+      tagName,
+      props,
+      child,
+      rightTagName,
+    };
+  };
+
+  const parseProps = () => {  // identifier
+    const props = [];
+
+    while (true) {  // identifier | >
+      if (token.kind === tokenKind.rightBracket) {  // >
+        break;
+      }
+
+      assert(tokenKind.identifier);
+      const propName = token;
+
+      nextToken();  // =
+      assert(tokenKind.equal);
+
+      nextToken();  // "
+      assert(tokenKind.quote);
+
+      nextToken();  // identifier
+      assert(tokenKind.identifier);
+      const propValue = token;
+
+      props.push({
+        name: propName,
+        value: propValue,
+      });
+
+      nextToken();  // "
+      assert(tokenKind.quote);
+
+      nextToken();  // identifier | >
+    }
+
+    return props;
+  };
+
+  const assert = (tokenKind) => {
+    if (token.kind === tokenKind) {
+      return;
+    }
+
+    const msg = `unexpected token: ${JSON.stringify(token)}`;
+    throw new Error(msg);
+  };
+
+  const nextToken = () => {
+    while (true) {
+      if (pos >= end) {
+        return token = createToken(tokenKind.eof, pos, pos, null);
+      }
+
+      let ch = code.charAt(pos);
+      switch (ch) {
+        case '<':
+          if (code.charAt(pos + 1) === '/') {
+            return token = createToken(tokenKind.leftBracketSlash, pos, pos += 2, '</');
+          }
+          return token = createToken(tokenKind.leftBracket, pos, ++pos, ch);
+
+        case '>':
+          return token = createToken(tokenKind.rightBracket, pos, ++pos, ch);
+
+        case '"':
+          return token = createToken(tokenKind.quote, pos, ++pos, ch);
+
+        case '=':
+          return token = createToken(tokenKind.equal, pos, ++pos, ch);
+
+        case ' ':
+        case '\n':
+          ++pos;
+          continue;
+
+        default:
+          return token = scanIdentifier();
+
+      }
+    }
+  };
+
+  const scanIdentifier = () => {
+    const identifierStart = pos;
+
+    while (true) {
+      if (pos >= end) {
+        break;
+      }
+
+      const ch = code.charAt(pos);
+      if (/[a-z]/.test(ch)) {
+        ++pos;
+        continue;
+      }
+
+      break;
+    }
+
+    const identifer = code.slice(identifierStart, pos);
+    return token = createToken(tokenKind.identifier, identifierStart, pos, identifer);
+  };
+
+  const createToken = (tokenKind, pos, end, sourceCode) => {
+    return {
+      kind: tokenKind,
+      pos,
+      end,
+      value: sourceCode,
+    };
+  };
+
+  return parse();
+};
+
+debugger
+const html = parser(code);
+debugger
\ No newline at end of file