2 files changed, 16 insertions, 0 deletions
diff --git a/src/util/identifier.rs b/src/util/identifier.rs
new file mode 100644
index 0000000..4887e02
--- /dev/null
+++ b/src/util/identifier.rs
@@ -0,0 +1,15 @@
+//! Info on JavaScript identifiers.
+
+use unicode_id::UnicodeID;
+
+/// Check if a character can start a JS identifier.
+pub fn id_start(char: char) -> bool {
+    UnicodeID::is_id_start(char) || matches!(char, '$' | '_')
+}
+
+/// Check if a character can continue a JS (or JSX) identifier.
+pub fn id_cont(char: char, jsx: bool) -> bool {
+    UnicodeID::is_id_continue(char)
+        || matches!(char, '\u{200c}' | '\u{200d}')
+        || (jsx && char == '-')
+}
diff --git a/src/util/mod.rs b/src/util/mod.rs
index edc7e14..ac93be0 100644
--- a/src/util/mod.rs
+++ b/src/util/mod.rs
@@ -6,6 +6,7 @@ pub mod constant;
 pub mod edit_map;
 pub mod encode;
 pub mod gfm_tagfilter;
+pub mod identifier;
 pub mod infer;
 pub mod mdx_collect;
 pub mod normalize_identifier;