TypeScriptToLua
diff --git a/‎src/LuaTransformer.ts‎
Lines changed: 7 additions & 1 deletion b/‎src/LuaTransformer.ts‎
Lines changed: 7 additions & 1 deletion
diff --git a/‎test/unit/identifiers.spec.ts‎
Lines changed: 43 additions & 0 deletions b/‎test/unit/identifiers.spec.ts‎
Lines changed: 43 additions & 0 deletions
@@ -4630,6 +4630,10 @@ export class LuaTransformer {
     }
 
     public transformIdentifier(identifier: ts.Identifier): tstl.Identifier {
+        if (identifier.escapedText === "globalThis") {
+            return tstl.createIdentifier("_G", identifier, this.getIdentifierSymbolId(identifier));
+        }
+
         if (identifier.originalKeywordKind === ts.SyntaxKind.UndefinedKeyword) {
             // TODO this is a hack that allows use to keep Identifier
             // as return time as changing that would break a lot of stuff.
@@ -5172,7 +5176,9 @@ export class LuaTransformer {
     protected hasUnsafeSymbolName(symbol: ts.Symbol, tsOriginal?: ts.Identifier): boolean {
         const isLuaKeyword = luaKeywords.has(symbol.name);
         const isInvalidIdentifier = !tsHelper.isValidLuaIdentifier(symbol.name);
-        const isAmbient = symbol.declarations.some(d => tsHelper.isAmbient(d));
+        // TODO investigate: declarations will be undefined if "globalThis" is passed, could be a TS bug
+        // WORKAROUND: added check for symbol.declarations
+        const isAmbient = symbol.declarations && symbol.declarations.some(d => tsHelper.isAmbient(d));
         if ((isLuaKeyword || isInvalidIdentifier) && isAmbient) {
             // Catch ambient declarations of identifiers with bad names
             throw TSTLErrors.InvalidAmbientIdentifierName(tsOriginal || ts.createIdentifier(symbol.name));
 
@@ -788,3 +788,46 @@ test("exported variable with lua keyword as name is not renamed", () => {
 
     expect(util.transpileExecuteAndReturnExport(code, "print")).toBe("foobar");
 });
+
+describe("globalThis translation", () => {
+    test("globalThis to _G (expression)", () => {
+        const code = `
+        var foo = "bar";
+        return globalThis.foo;`;
+    
+        const lua = util.transpileString(code);
+    
+        expect(util.executeLua(lua)).toBe("bar");
+    });
+
+    test("globalThis to _G (assign)", () => {
+        const code = `
+        globalThis.foo = "bar";
+        return globalThis.foo;`;
+    
+        const lua = util.transpileString(code);
+    
+        expect(util.executeLua(lua)).toBe("bar");
+    });
+
+    test("globalThis to _G (reassign)", () => {
+        const code = `
+        globalThis.foo = "bar";
+        globalThis.foo = "baz";
+        return globalThis.foo;`;
+    
+        const lua = util.transpileString(code);
+    
+        expect(util.executeLua(lua)).toBe("baz");
+    });
+
+    test("globalThis to _G (function)", () => {
+        const code = `
+        globalThis.foo = () => "bar";
+        return globalThis.foo();`;
+    
+        const lua = util.transpileString(code);
+    
+        expect(util.executeLua(lua)).toBe("bar");
+    });
+});