It... worked!

package.json

@@ -6,7 +6,7 @@
 	"scripts": {
 		"build": "babel -d ./lib ./src",
 		"prepublish": "babel -d ./lib ./src --minified",
-		"test": "babel --no-babelrc --plugins=./lib/index.js test.js --out-file test.opt.js"
+		"test": "babel --no-babelrc --plugins=./lib/index.js test.ts --out-file test.opt.js"
 	},
 	"repository": {
 		"type": "git",
@@ -19,7 +19,9 @@
 	},
 	"homepage": "https://github.com/vihanb/babel-plugin-loop-optimizer#readme",
 	"devDependencies": {
-		"babel-cli": "next",
-		"babel-preset-env": "next"
+		"@babel/core": "latest",
+		"@babel/preset-env": "latest",
+		"@babel/preset-typescript": "latest",
+		"@babel/cli": "latest"
 	}
 }

test.opt.js

@@ -1,11 +1,11 @@
 {
   console.log("FORWARD");
-  let ar = [1, 2, 3]; // loop-optimizer: FORWARD
+  let ar = [1, 2, 3]; // loop-optimizer: FORWARD, POSSIBLE_UNDEFINED
 
   let _a = ar;
   let _f = console.log;
 
-  for (let _i = 0; _i < _a.length; _i++) {
+  for (let _i = 0; _i < _a.length && _a[_i] !== undefined; _i++) {
     _f(_a[_i], _i, _a);
   }
 }

test.ts

@@ -0,0 +1,20 @@
+{
+    console.log("FORWARD")
+    let ar = [1,2,3]
+    // loop-optimizer: FORWARD, POSSIBLE_UNDEFINED
+    ar.forEach(console.log)
+}
+
+{
+    console.log("KEEP")
+    let ar = [1,2,3]
+    // loop-optimizer: KEEP
+    ar.forEach(console.log)
+}
+
+{
+    console.log("nothing")
+    let ar = [1,2,3]
+    // nothing
+    ar.forEach(console.log)
+}