remove undefined initialization. Closes #869

fabiosantoscode · fabiosantoscode · commit 36349ecb32ed · 2020-11-14T15:47:29.000Z
diff --git a/lib/compress/index.js b/lib/compress/index.js
@@ -5085,6 +5085,17 @@ def_optimize(AST_Definitions, function(self) {
     return self;
 });
 
+def_optimize(AST_VarDef, function(self) {
+    if (
+        self.name instanceof AST_SymbolLet
+        && self.value != null
+        && is_undefined(self.value)
+    ) {
+        self.value = null;
+    }
+    return self;
+});
+
 def_optimize(AST_Import, function(self) {
     return self;
 });
diff --git a/test/compress/block-scope.js b/test/compress/block-scope.js
@@ -31,6 +31,17 @@ do_not_hoist_let: {
     }
 }
 
+drop_undefined_vardef: {
+    input: {
+        let x = undefined;
+        const y = undefined;
+    }
+    expect: {
+        let x;
+        const y = void 0;
+    }
+}
+
 do_not_remove_anon_blocks_if_they_have_decls: {
     input: {
         function x() {
