From 35203feb95c8eaa71a3566e1f6a66f7f16d72871 Mon Sep 17 00:00:00 2001
From: EGOIST <0x142857@gmail.com>
Date: Mon, 20 Jul 2020 16:51:37 +0800
Subject: [PATCH 1/9] chore: upgrade to tsup 3.0

---
 package.json |  4 ++--
 yarn.lock    | 35 +++++++++--------------------------
 2 files changed, 11 insertions(+), 28 deletions(-)

diff --git a/package.json b/package.json
index dbe28305..5f453eef 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,7 @@
     "url": "https://github.com/egoist/tsup.git"
   },
   "scripts": {
-    "build": "rm -rf dist && tsup src/cli.ts src/index.ts src/rollup.ts --external typescript --bundle --dts",
+    "build": "rm -rf dist && tsup src/cli.ts src/index.ts src/rollup.ts --dts",
     "prepublishOnly": "npm run build",
     "test": "npm run build && jest"
   },
@@ -39,7 +39,7 @@
     "prettier": "^2.0.5",
     "rollup-plugin-hashbang": "^2.2.2",
     "ts-jest": "^26.1.2",
-    "tsup": "^2.1.0",
+    "tsup": "^3.0.0",
     "typescript": "^3.9.6"
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 2f957e90..ca346338 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -484,7 +484,7 @@
   dependencies:
     "@rollup/pluginutils" "^3.0.8"
 
-"@rollup/pluginutils@^3.0.8", "@rollup/pluginutils@^3.1.0":
+"@rollup/pluginutils@^3.0.8":
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/@rollup/pluginutils/-/pluginutils-3.1.0.tgz#706b4524ee6dc8b103b3c995533e5ad680c02b9b"
   integrity sha512-GksZ6pr6TpIjHm8h9lSQ8pi8BE9VeubNT0OMJ3B5uZJ8pz73NPiqOtCog/x2/QzM1ENChPKxMDhiQuRHsqc+lg==
@@ -1309,11 +1309,6 @@ error-ex@^1.3.1:
   dependencies:
     is-arrayish "^0.2.1"
 
-esbuild@^0.6.3:
-  version "0.6.3"
-  resolved "https://registry.yarnpkg.com/esbuild/-/esbuild-0.6.3.tgz#a957e22f2503c745793514388110f9b55b3a6f83"
-  integrity sha512-4lHgz/EvGLRQnDYzzrvW+eilaPHim5pCLz4mP0k0QIalD/n8Ji2NwQwoIa1uX+yKkbn9R/FAZvaEbodjx55rDg==
-
 esbuild@^0.6.4:
   version "0.6.5"
   resolved "https://registry.yarnpkg.com/esbuild/-/esbuild-0.6.5.tgz#efbe11cf51abd0d4d489ca1bc80fd4761a35bd16"
@@ -3143,15 +3138,6 @@ rollup-plugin-dts@^1.4.8:
   optionalDependencies:
     "@babel/code-frame" "^7.10.4"
 
-rollup-plugin-esbuild@^2.4.1:
-  version "2.4.1"
-  resolved "https://registry.yarnpkg.com/rollup-plugin-esbuild/-/rollup-plugin-esbuild-2.4.1.tgz#6e05850e3051a56811b2f491e2243272701b060d"
-  integrity sha512-UyL3LKbh4DxV8VZCzEw3kZB/z+vhkIXSMT8Y5JzOMc/PI3FGA6w94vSRl68IZUsS1hLxG1NB+W+0ck/9fDLk3A==
-  dependencies:
-    "@rollup/pluginutils" "^3.1.0"
-    joycon "^2.2.5"
-    strip-json-comments "^3.1.1"
-
 rollup-plugin-hashbang@^2.2.2:
   version "2.2.2"
   resolved "https://registry.yarnpkg.com/rollup-plugin-hashbang/-/rollup-plugin-hashbang-2.2.2.tgz#971fc49b452e63f9dfdc75f79ae7256b3485e750"
@@ -3470,11 +3456,6 @@ strip-final-newline@^2.0.0:
   resolved "https://registry.yarnpkg.com/strip-final-newline/-/strip-final-newline-2.0.0.tgz#89b852fb2fcbe936f6f4b3187afb0a12c1ab58ad"
   integrity sha512-BrpvfNAE3dcvq7ll3xVumzjKjZQ5tI1sEUIKr3Uoks0XUl45St3FlatVqef9prk4jRDzhW6WZg+3bk93y6pLjA==
 
-strip-json-comments@^3.1.1:
-  version "3.1.1"
-  resolved "https://registry.yarnpkg.com/strip-json-comments/-/strip-json-comments-3.1.1.tgz#31f1281b3832630434831c310c01cccda8cbe006"
-  integrity sha512-6fPc+R4ihwqP6N/aIv2f1gMH8lOVtWQHoqC4yK6oSDVVocumAsfCqjkXnqiYMhmMwS/mEHLp7Vehlt3ql6lEig==
-
 sucrase@^3.15.0:
   version "3.15.0"
   resolved "https://registry.yarnpkg.com/sucrase/-/sucrase-3.15.0.tgz#78596a78be7264a65b52ed8d873883413ef0220c"
@@ -3637,17 +3618,19 @@ ts-jest@^26.1.2:
     semver "7.x"
     yargs-parser "18.x"
 
-tsup@^2.1.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/tsup/-/tsup-2.1.0.tgz#2d6410d38a62e28a20eb6cb863fe5590b5488b3c"
-  integrity sha512-olm/SXqV58FUczleRXRuZiUB3odEbH+BH+AQGZgW8PgTkCKjN+MIvw7T6KewH6Y0guUFkJJw7M4q8EMYjaIioA==
+tsup@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/tsup/-/tsup-3.0.0.tgz#2474176b35fcebfdd4a48f17e7d302946f45830f"
+  integrity sha512-R4nwIEiR7SiTFl92wk5OHFetJvIUFPDJu3HlMpOnAVrza8YlrK4zyYbfSUaV8M9w4f2z2+HE246L4CRjLWIeQA==
   dependencies:
     cac "^6.5.13"
-    esbuild "^0.6.3"
+    chalk "^4.1.0"
+    chokidar "^3.4.1"
+    esbuild "^0.6.4"
     joycon "^2.2.5"
     rollup "^2.21.0"
     rollup-plugin-dts "^1.4.8"
-    rollup-plugin-esbuild "^2.4.1"
+    sucrase "^3.15.0"
 
 tunnel-agent@^0.6.0:
   version "0.6.0"

From a3ac5bf49805ec527a9170114d07e0e2b38229cd Mon Sep 17 00:00:00 2001
From: EGOIST <0x142857@gmail.com>
Date: Mon, 20 Jul 2020 16:53:01 +0800
Subject: [PATCH 2/9] chore: no longer support --dts-bundle

---
 README.md | 2 --
 1 file changed, 2 deletions(-)

diff --git a/README.md b/README.md
index 33ff5702..6aee9c43 100644
--- a/README.md
+++ b/README.md
@@ -51,8 +51,6 @@ tsup index.ts --dts
 
 This will emit `./dist/index.js` and `./dist/index.d.ts`.
 
-If you want to bundle types from `node_modules` as well, use the `--dts-bundle` flag instead, which implicitly set `--dts` flag as well. (Note that this is experimental.)
-
 ### Bundle formats
 
 Supported format: `esm`, `cjs`, (default) and `iife`.

From c3b88aeac73407dfbe6a89b40c8a6ab8c2794e54 Mon Sep 17 00:00:00 2001
From: "dependabot-preview[bot]"
 <27856297+dependabot-preview[bot]@users.noreply.github.com>
Date: Mon, 20 Jul 2020 21:25:26 +0000
Subject: [PATCH 3/9] chore(deps): [security] bump lodash from 4.17.15 to
 4.17.19 (#73)

---
 yarn.lock | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/yarn.lock b/yarn.lock
index ca346338..3f2675b6 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2541,9 +2541,9 @@ lodash.sortby@^4.7.0:
   integrity sha1-7dFMgk4sycHgsKG0K7UhBRakJDg=
 
 lodash@^4.17.13, lodash@^4.17.15:
-  version "4.17.15"
-  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.15.tgz#b447f6670a0455bbfeedd11392eff330ea097548"
-  integrity sha512-8xOcRHvCjnocdS5cpwXQXVzmmh5e5+saE2QGoeQmbKmRS6J3VQppPOIt0MnmE+4xlZoumy0GPG0D0MVIQbNA1A==
+  version "4.17.19"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.19.tgz#e48ddedbe30b3321783c5b4301fbd353bc1e4a4b"
+  integrity sha512-JNvd8XER9GQX0v2qJgsaN/mzFCNA5BRe/j8JN9d+tWyGLSodKQHKFicdwNYzWwI3wjRnaKPsGj1XkBjx/F96DQ==
 
 magic-string@^0.22.4:
   version "0.22.5"

From f16372e84aa3cbe39e1f0fddd5bc195dd7ae36ad Mon Sep 17 00:00:00 2001
From: "dependabot-preview[bot]"
 <27856297+dependabot-preview[bot]@users.noreply.github.com>
Date: Mon, 20 Jul 2020 21:26:05 +0000
Subject: [PATCH 4/9] chore(deps): bump cac from 6.5.13 to 6.6.1 (#74)

---
 package.json | 2 +-
 yarn.lock    | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/package.json b/package.json
index 5f453eef..808d2401 100644
--- a/package.json
+++ b/package.json
@@ -18,7 +18,7 @@
     "test": "npm run build && jest"
   },
   "dependencies": {
-    "cac": "^6.5.13",
+    "cac": "^6.6.1",
     "chalk": "^4.1.0",
     "chokidar": "^3.4.1",
     "esbuild": "^0.6.4",
diff --git a/yarn.lock b/yarn.lock
index 3f2675b6..32d03d7b 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -936,10 +936,10 @@ buffer-from@1.x, buffer-from@^1.0.0:
   resolved "https://registry.yarnpkg.com/buffer-from/-/buffer-from-1.1.1.tgz#32713bc028f75c02fdb710d7c7bcec1f2c6070ef"
   integrity sha512-MQcXEUbCKtEo7bhqEs6560Hyd4XaovZlO/k9V3hjVUF/zwW7KBVdSK4gIt/bzwS9MbR5qob+F5jusZsb0YQK2A==
 
-cac@^6.5.13:
-  version "6.5.13"
-  resolved "https://registry.yarnpkg.com/cac/-/cac-6.5.13.tgz#8d9be6dce0afb707c76c5962bf9cc6571f4c933a"
-  integrity sha512-pt643//kQb3S6syXMJ/EIfNZpivKeFpCdnnPbJ3Iq9ZVZyXQcQjXvzVMWTEQuUspp+rHUlhZYZZfnviP88VuYA==
+cac@^6.5.13, cac@^6.6.1:
+  version "6.6.1"
+  resolved "https://registry.yarnpkg.com/cac/-/cac-6.6.1.tgz#3dde3f6943f45d42a56729ea3573c08b3e7b6a6d"
+  integrity sha512-uhki4T3Ax68hw7Dufi0bATVAF8ayBSwOKUEJHjObPrUN4tlQ8Lf7oljpTje/mArLxYN0D743c2zJt4C1bVTCqg==
 
 cache-base@^1.0.1:
   version "1.0.1"

From 42c7d9b7365d1ba1e0b22bab6d1f163dfe797760 Mon Sep 17 00:00:00 2001
From: "dependabot-preview[bot]"
 <27856297+dependabot-preview[bot]@users.noreply.github.com>
Date: Mon, 20 Jul 2020 21:26:36 +0000
Subject: [PATCH 5/9] chore(deps-dev): bump typescript from 3.9.6 to 3.9.7
 (#77)

---
 package.json | 2 +-
 yarn.lock    | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/package.json b/package.json
index 808d2401..8e0a491e 100644
--- a/package.json
+++ b/package.json
@@ -40,6 +40,6 @@
     "rollup-plugin-hashbang": "^2.2.2",
     "ts-jest": "^26.1.2",
     "tsup": "^3.0.0",
-    "typescript": "^3.9.6"
+    "typescript": "^3.9.7"
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 32d03d7b..2052799b 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3678,10 +3678,10 @@ typedarray-to-buffer@^3.1.5:
   dependencies:
     is-typedarray "^1.0.0"
 
-typescript@^3.9.6:
-  version "3.9.6"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.9.6.tgz#8f3e0198a34c3ae17091b35571d3afd31999365a"
-  integrity sha512-Pspx3oKAPJtjNwE92YS05HQoY7z2SFyOpHo9MqJor3BXAGNaPUs83CuVp9VISFkSjyRfiTpmKuAYGJB7S7hOxw==
+typescript@^3.9.7:
+  version "3.9.7"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.9.7.tgz#98d600a5ebdc38f40cb277522f12dc800e9e25fa"
+  integrity sha512-BLbiRkiBzAwsjut4x/dsibSTB6yWpwT5qWmC2OfuCg3GgVQCSgMs4vEctYPhsaGtd0AeuuHMkjZ2h2WG8MSzRw==
 
 union-value@^1.0.0:
   version "1.0.1"

From 8b52a5751d277e296a8bf4b2fd0d866afabcbea3 Mon Sep 17 00:00:00 2001
From: "dependabot-preview[bot]"
 <27856297+dependabot-preview[bot]@users.noreply.github.com>
Date: Mon, 20 Jul 2020 21:26:42 +0000
Subject: [PATCH 6/9] chore(deps-dev): bump @types/jest from 26.0.4 to 26.0.5
 (#75)

---
 package.json | 2 +-
 yarn.lock    | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/package.json b/package.json
index 8e0a491e..b4d3b861 100644
--- a/package.json
+++ b/package.json
@@ -30,7 +30,7 @@
   "devDependencies": {
     "@rollup/plugin-json": "^4.1.0",
     "@types/fs-extra": "^9.0.1",
-    "@types/jest": "^26.0.4",
+    "@types/jest": "^26.0.5",
     "@types/node": "^14.0.23",
     "@types/resolve": "^1.17.1",
     "execa": "^4.0.3",
diff --git a/yarn.lock b/yarn.lock
index 2052799b..32572332 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -595,10 +595,10 @@
     "@types/istanbul-lib-coverage" "*"
     "@types/istanbul-lib-report" "*"
 
-"@types/jest@^26.0.4":
-  version "26.0.4"
-  resolved "https://registry.yarnpkg.com/@types/jest/-/jest-26.0.4.tgz#d2e513e85aca16992816f192582b5e67b0b15efb"
-  integrity sha512-4fQNItvelbNA9+sFgU+fhJo8ZFF+AS4Egk3GWwCW2jFtViukXbnztccafAdLhzE/0EiCogljtQQXP8aQ9J7sFg==
+"@types/jest@^26.0.5":
+  version "26.0.5"
+  resolved "https://registry.yarnpkg.com/@types/jest/-/jest-26.0.5.tgz#23a8eecf4764a770ea8d3a0d1ea16b96c822035d"
+  integrity sha512-heU+7w8snfwfjtcj2H458aTx3m5unIToOJhx75ebHilBiiQ39OIdA18WkG4LP08YKeAoWAGvWg8s+22w/PeJ6w==
   dependencies:
     jest-diff "^25.2.1"
     pretty-format "^25.2.1"

From 1d03de78e1cc63a465d0b2226ba9aff55b5ec735 Mon Sep 17 00:00:00 2001
From: "dependabot-preview[bot]"
 <27856297+dependabot-preview[bot]@users.noreply.github.com>
Date: Mon, 20 Jul 2020 21:29:37 +0000
Subject: [PATCH 7/9] chore(deps): bump rollup from 2.21.0 to 2.22.1 (#78)

---
 package.json | 2 +-
 yarn.lock    | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/package.json b/package.json
index b4d3b861..ae715ce2 100644
--- a/package.json
+++ b/package.json
@@ -23,7 +23,7 @@
     "chokidar": "^3.4.1",
     "esbuild": "^0.6.4",
     "joycon": "^2.2.5",
-    "rollup": "^2.21.0",
+    "rollup": "^2.22.1",
     "rollup-plugin-dts": "^1.4.8",
     "sucrase": "^3.15.0"
   },
diff --git a/yarn.lock b/yarn.lock
index 32572332..8c828d14 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3145,10 +3145,10 @@ rollup-plugin-hashbang@^2.2.2:
   dependencies:
     magic-string "^0.22.4"
 
-rollup@^2.21.0:
-  version "2.21.0"
-  resolved "https://registry.yarnpkg.com/rollup/-/rollup-2.21.0.tgz#d2e114533812043d5c9b7b0a83f1b2a242e4e1d6"
-  integrity sha512-BEGgy+wSzux7Ycq58pRiWEOBZaXRXTuvzl1gsm7gqmsAHxkWf9nyA5V2LN9fGSHhhDQd0/C13iRzSh4bbIpWZQ==
+rollup@^2.21.0, rollup@^2.22.1:
+  version "2.22.1"
+  resolved "https://registry.yarnpkg.com/rollup/-/rollup-2.22.1.tgz#8700522aa5feb12c6bd51810df8a276699d136b1"
+  integrity sha512-K9AUQUCJkVqC+A7uUDacfhmpEeAjc2uOmSpvGI5xaYsm8pXgy4ZWEM8wHPfKj11xvCwFZppkRDo8a0RESJXCnw==
   optionalDependencies:
     fsevents "~2.1.2"
 

From 4f36b9df1a1760c085c38dd403d1882bc3c2ba29 Mon Sep 17 00:00:00 2001
From: "dependabot-preview[bot]"
 <27856297+dependabot-preview[bot]@users.noreply.github.com>
Date: Mon, 20 Jul 2020 21:29:54 +0000
Subject: [PATCH 8/9] chore(deps-dev): bump ts-jest from 26.1.2 to 26.1.3 (#76)

---
 package.json | 2 +-
 yarn.lock    | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/package.json b/package.json
index ae715ce2..3dc6c0f9 100644
--- a/package.json
+++ b/package.json
@@ -38,7 +38,7 @@
     "jest": "^26.1.0",
     "prettier": "^2.0.5",
     "rollup-plugin-hashbang": "^2.2.2",
-    "ts-jest": "^26.1.2",
+    "ts-jest": "^26.1.3",
     "tsup": "^3.0.0",
     "typescript": "^3.9.7"
   }
diff --git a/yarn.lock b/yarn.lock
index 8c828d14..2afcaece 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3602,10 +3602,10 @@ ts-interface-checker@^0.1.9:
   resolved "https://registry.yarnpkg.com/ts-interface-checker/-/ts-interface-checker-0.1.11.tgz#07e7eddb08212f83fef12c253d0cefa8c70fe1bc"
   integrity sha512-Jx6cFBiuCQrRl3CgoIOamIE/toZ8jQJbIlsLGpkBiUpCEUyFcyZ2pvjP8kSXIcz8V5v/murgm/5EfIQapUmh6A==
 
-ts-jest@^26.1.2:
-  version "26.1.2"
-  resolved "https://registry.yarnpkg.com/ts-jest/-/ts-jest-26.1.2.tgz#dd2e832ffae9cb803361483b6a3010a6413dc475"
-  integrity sha512-V4SyBDO9gOdEh+AF4KtXJeP+EeI4PkOrxcA8ptl4o8nCXUVM5Gg/8ngGKneS5BsZaR9DXVQNqj9k+iqGAnpGow==
+ts-jest@^26.1.3:
+  version "26.1.3"
+  resolved "https://registry.yarnpkg.com/ts-jest/-/ts-jest-26.1.3.tgz#aac928a05fdf13e3e6dfbc8caec3847442667894"
+  integrity sha512-beUTSvuqR9SmKQEylewqJdnXWMVGJRFqSz2M8wKJe7GBMmLZ5zw6XXKSJckbHNMxn+zdB3guN2eOucSw2gBMnw==
   dependencies:
     bs-logger "0.x"
     buffer-from "1.x"

From 0ebb08dd8ec70c13ec09b05c8fb33d87d83ff2ec Mon Sep 17 00:00:00 2001
From: EGOIST <0x142857@gmail.com>
Date: Tue, 21 Jul 2020 15:17:02 +0800
Subject: [PATCH 9/9] feat: add es5 target

---
 README.md                             |   4 +
 package.json                          |   5 +-
 src/index.ts                          |  68 +++++++++++----
 src/utils.ts                          |  16 +++-
 test/__snapshots__/index.test.ts.snap |  14 +++
 test/index.test.ts                    |  26 +++++-
 yarn.lock                             | 118 +++++++++++++++++++++++++-
 7 files changed, 228 insertions(+), 23 deletions(-)

diff --git a/README.md b/README.md
index 6aee9c43..2b973695 100644
--- a/README.md
+++ b/README.md
@@ -72,6 +72,10 @@ dist
 └── index.js
 ```
 
+### ES5 support
+
+You can `--target es5` or `"target": "es5" in `tsconfig.json` to compile the code down to es5, it's processed by [buble](http://buble.surge.sh/). Some features are supported by this target, namely: `for .. of`.
+
 ### Watch mode
 
 ```bash
diff --git a/package.json b/package.json
index 3dc6c0f9..c5232d8e 100644
--- a/package.json
+++ b/package.json
@@ -29,6 +29,7 @@
   },
   "devDependencies": {
     "@rollup/plugin-json": "^4.1.0",
+    "@types/buble": "^0.19.2",
     "@types/fs-extra": "^9.0.1",
     "@types/jest": "^26.0.5",
     "@types/node": "^14.0.23",
@@ -40,6 +41,8 @@
     "rollup-plugin-hashbang": "^2.2.2",
     "ts-jest": "^26.1.3",
     "tsup": "^3.0.0",
-    "typescript": "^3.9.7"
+    "typescript": "^3.9.7",
+    "strip-json-comments": "^3.1.1",
+    "buble": "^0.20.0"
   }
 }
diff --git a/src/index.ts b/src/index.ts
index f4539300..878f28b5 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -2,9 +2,11 @@ import fs from 'fs'
 import { dirname, join } from 'path'
 import { Worker } from 'worker_threads'
 import colors from 'chalk'
+import { transform as transformToEs5 } from 'buble'
 import { Service, startService, BuildResult } from 'esbuild'
-import { getDeps, resolveTsConfig } from './utils'
+import { getDeps, loadTsConfig } from './utils'
 import { FSWatcher } from 'chokidar'
+import { PrettyError } from './errors'
 
 const textDecoder = new TextDecoder('utf-8')
 
@@ -63,11 +65,13 @@ export async function runEsbuild(
         globalName: options.globalName,
         jsxFactory: options.jsxFactory,
         jsxFragment: options.jsxFragment,
+        target: options.target === 'es5' ? 'es2016' : options.target,
         define: options.define,
         external,
         outdir: format === 'cjs' ? outDir : join(outDir, format),
         write: false,
         splitting: format === 'cjs' || format === 'esm',
+        logLevel: 'error'
       }))
     const timeInMs = Date.now() - startTime
     console.log(
@@ -91,25 +95,41 @@ export async function runEsbuild(
       result.outputFiles.map(async (file) => {
         const dir = dirname(file.path)
         const outPath = file.path
+        if (!outPath.endsWith('.js')) return
         await fs.promises.mkdir(dir, { recursive: true })
         let mode: number | undefined
         if (file.contents[0] === 35 && file.contents[1] === 33) {
           mode = 0o755
         }
+        let contents = textDecoder.decode(file.contents)
+        if (options.target === 'es5') {
+          try {
+            contents = transformToEs5(contents, {
+              source: file.path,
+              file: file.path,
+              transforms: {
+                modules: false,
+                arrow: true,
+                dangerousTaggedTemplateString: true,
+                spreadRest: true,
+              },
+            }).code
+          } catch (error) {
+            throw new PrettyError(
+              `Error compiling to es5 target:\n${error.snippet}`
+            )
+          }
+        }
         // Cause we need to transform to code from esm to cjs first
-        if (format === 'cjs' && outPath.endsWith('.js')) {
-          const content = transform(textDecoder.decode(file.contents), {
+        if (format === 'cjs') {
+          contents = transform(contents, {
             transforms: ['imports'],
-          })
-          await fs.promises.writeFile(outPath, content.code, {
-            encoding: 'utf8',
-            mode,
-          })
-        } else {
-          await fs.promises.writeFile(outPath, file.contents, {
-            mode,
-          })
+          }).code
         }
+        await fs.promises.writeFile(outPath, contents, {
+          encoding: 'utf8',
+          mode,
+        })
       })
     )
   }
@@ -124,6 +144,8 @@ function stopServices() {
 }
 
 export async function build(options: Options) {
+  options = { ...options }
+
   let watcher: FSWatcher | undefined
   let runServices: Array<() => Promise<BuildResult | void>> | undefined
 
@@ -150,10 +172,24 @@ export async function build(options: Options) {
   }
 
   try {
-    const tsconfig = resolveTsConfig(process.cwd())
-    if (tsconfig) {
-      console.log(makeLabel('CLI', 'info'), `Using tsconfig: ${tsconfig}`)
+    const tsconfig = await loadTsConfig(process.cwd())
+    if (tsconfig.path && tsconfig.data) {
+      console.log(makeLabel('CLI', 'info'), `Using tsconfig: ${tsconfig.path}`)
+      if (!options.target) {
+        options.target = tsconfig.data.compilerOptions?.target
+      }
+      if (!options.jsxFactory) {
+        options.jsxFactory = tsconfig.data.compilerOptions?.jsxFactory
+      }
+      if (!options.jsxFragment) {
+        options.jsxFragment = tsconfig.data.compilerOptions?.jsxFragmentFactory
+      }
+    }
+
+    if (!options.target) {
+      options.target = 'es2018'
     }
+    console.log(makeLabel('CLI', 'info'), `Target: ${options.target}`)
 
     runServices = await Promise.all([
       ...options.format.map((format) => runEsbuild(options, { format })),
@@ -164,7 +200,7 @@ export async function build(options: Options) {
       worker.postMessage({
         options,
       })
-      worker.on('message', data => {
+      worker.on('message', (data) => {
         if (data === 'exit') {
           worker.unref()
         }
diff --git a/src/utils.ts b/src/utils.ts
index 81a4cadc..6dc40c02 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,7 +1,19 @@
+import fs from 'fs'
 import JoyCon from 'joycon'
+import stripJsonComments from 'strip-json-comments'
 
 const joycon = new JoyCon()
 
+joycon.addLoader({
+  test: /\.json$/,
+  async load(filepath) {
+    const content = stripJsonComments(
+      await fs.promises.readFile(filepath, 'utf8')
+    )
+    return JSON.parse(content)
+  },
+})
+
 // No backslash in path
 function slash(input: string) {
   return input.replace(/\\/g, '/')
@@ -45,8 +57,8 @@ export function isExternal(
   return false
 }
 
-export function resolveTsConfig(cwd: string) {
-  return joycon.resolveSync(['tsconfig.build.json', 'tsconfig.json'], cwd)
+export function loadTsConfig(cwd: string) {
+  return joycon.load(['tsconfig.build.json', 'tsconfig.json'], cwd)
 }
 
 export async function getDeps(cwd: string) {
diff --git a/test/__snapshots__/index.test.ts.snap b/test/__snapshots__/index.test.ts.snap
index 6910f29e..b54c74ed 100644
--- a/test/__snapshots__/index.test.ts.snap
+++ b/test/__snapshots__/index.test.ts.snap
@@ -1,5 +1,19 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`es5 target 1`] = `
+"\\"use strict\\";Object.defineProperty(exports, \\"__esModule\\", {value: true});// input.ts
+var Foo = function Foo () {};
+
+Foo.prototype.hi = function hi () {
+  var a = function () { return \\"foo\\"; };
+  console.log(a());
+};
+
+
+exports.Foo = Foo;
+"
+`;
+
 exports[`simple 1`] = `
 "\\"use strict\\";Object.defineProperty(exports, \\"__esModule\\", {value: true});// foo.ts
 var foo_default = \\"foo\\";
diff --git a/test/index.test.ts b/test/index.test.ts
index ce7594ea..202b35c6 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -24,14 +24,16 @@ function runTest(
         return fs.outputFile(join(testDir, name), files[name], 'utf8')
       })
     )
-    const { exitCode } = await execa(
+    const { exitCode, stdout, stderr } = await execa(
       bin,
       ['input.ts', ...(options.flags || [])],
       {
         cwd: testDir,
       }
     )
-    expect(exitCode).toBe(0)
+    if (exitCode !== 0) {
+      throw new Error(stdout + stderr)
+    }
     if (options.snapshot !== false) {
       const output = await fs.readFile(join(testDir, 'dist/input.js'), 'utf8')
       expect(output).toMatchSnapshot()
@@ -51,6 +53,24 @@ runTest(
   },
   {
     snapshot: false,
-    flags: ['--dts']
+    flags: ['--dts'],
+  }
+)
+
+runTest(
+  'es5 target',
+  {
+    'input.ts': `
+  export class Foo {
+    hi (): void {
+      let a = () => 'foo'
+
+      console.log(a())
+    }
+  }
+  `,
+  },
+  {
+    flags: ['--target', 'es5'],
   }
 )
diff --git a/yarn.lock b/yarn.lock
index 2afcaece..02cffa46 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -551,6 +551,13 @@
   dependencies:
     "@babel/types" "^7.3.0"
 
+"@types/buble@^0.19.2":
+  version "0.19.2"
+  resolved "https://registry.yarnpkg.com/@types/buble/-/buble-0.19.2.tgz#a4289d20b175b3c206aaad80caabdabe3ecdfdd1"
+  integrity sha512-uUD8zIfXMKThmFkahTXDGI3CthFH1kMg2dOm3KLi4GlC5cbARA64bEcUMbbWdWdE73eoc/iBB9PiTMqH0dNS2Q==
+  dependencies:
+    magic-string "^0.25.0"
+
 "@types/color-name@^1.1.1":
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/@types/color-name/-/color-name-1.1.1.tgz#1c1261bbeaa10a8055bbc5d8ab84b7b2afc846a0"
@@ -647,6 +654,11 @@ abab@^2.0.3:
   resolved "https://registry.yarnpkg.com/abab/-/abab-2.0.3.tgz#623e2075e02eb2d3f2475e49f99c91846467907a"
   integrity sha512-tsFzPpcttalNjFBCFMqsKYQcWxxen1pgJR56by//QwvJc4/OUS3kPOOttx2tSIfjsylB0pYu7f5D3K1RCxUnUg==
 
+acorn-dynamic-import@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/acorn-dynamic-import/-/acorn-dynamic-import-4.0.0.tgz#482210140582a36b83c3e342e1cfebcaa9240948"
+  integrity sha512-d3OEjQV4ROpoflsnUA8HozoIR504TFxNivYEUi6uwz0IYhBkTDXGuWlNdMtybRt3nqVx/L6XqMt0FxkXuWKZhw==
+
 acorn-globals@^6.0.0:
   version "6.0.0"
   resolved "https://registry.yarnpkg.com/acorn-globals/-/acorn-globals-6.0.0.tgz#46cdd39f0f8ff08a876619b55f5ac8a6dc770b45"
@@ -655,11 +667,21 @@ acorn-globals@^6.0.0:
     acorn "^7.1.1"
     acorn-walk "^7.1.1"
 
+acorn-jsx@^5.2.0:
+  version "5.2.0"
+  resolved "https://registry.yarnpkg.com/acorn-jsx/-/acorn-jsx-5.2.0.tgz#4c66069173d6fdd68ed85239fc256226182b2ebe"
+  integrity sha512-HiUX/+K2YpkpJ+SzBffkM/AQ2YE03S0U1kjTLVpoJdhZMOWy8qvXVN9JdLqv2QsaQ6MPYQIuNmwD8zOiYUofLQ==
+
 acorn-walk@^7.1.1:
   version "7.1.1"
   resolved "https://registry.yarnpkg.com/acorn-walk/-/acorn-walk-7.1.1.tgz#345f0dffad5c735e7373d2fec9a1023e6a44b83e"
   integrity sha512-wdlPY2tm/9XBr7QkKlq0WQVgiuGTX6YWPyRyBviSoScBuLfTVQhvwg6wJ369GJ/1nPfTLMfnrFIfjqVg6d+jQQ==
 
+acorn@^6.4.1:
+  version "6.4.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.1.tgz#531e58ba3f51b9dacb9a6646ca4debf5b14ca474"
+  integrity sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==
+
 acorn@^7.1.1:
   version "7.2.0"
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-7.2.0.tgz#17ea7e40d7c8640ff54a694c889c26f31704effe"
@@ -931,6 +953,19 @@ bser@2.1.1:
   dependencies:
     node-int64 "^0.4.0"
 
+buble@^0.20.0:
+  version "0.20.0"
+  resolved "https://registry.yarnpkg.com/buble/-/buble-0.20.0.tgz#a143979a8d968b7f76b57f38f2e7ce7cfe938d1f"
+  integrity sha512-/1gnaMQE8xvd5qsNBl+iTuyjJ9XxeaVxAMF86dQ4EyxFJOZtsgOS8Ra+7WHgZTam5IFDtt4BguN0sH0tVTKrOw==
+  dependencies:
+    acorn "^6.4.1"
+    acorn-dynamic-import "^4.0.0"
+    acorn-jsx "^5.2.0"
+    chalk "^2.4.2"
+    magic-string "^0.25.7"
+    minimist "^1.2.5"
+    regexpu-core "4.5.4"
+
 buffer-from@1.x, buffer-from@^1.0.0:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/buffer-from/-/buffer-from-1.1.1.tgz#32713bc028f75c02fdb710d7c7bcec1f2c6070ef"
@@ -983,7 +1018,7 @@ caseless@~0.12.0:
   resolved "https://registry.yarnpkg.com/caseless/-/caseless-0.12.0.tgz#1b681c21ff84033c826543090689420d187151dc"
   integrity sha1-G2gcIf+EAzyCZUMJBolCDRhxUdw=
 
-chalk@^2.0.0:
+chalk@^2.0.0, chalk@^2.4.2:
   version "2.4.2"
   resolved "https://registry.yarnpkg.com/chalk/-/chalk-2.4.2.tgz#cd42541677a54333cf541a49108c1432b44c9424"
   integrity sha512-Mti+f9lpJNcwF4tWV8/OrTTtF1gZi+f8FqlyAdouralcFWFQWF2+NgCHShjkCb+IFBLq9buZwE1xckQU4peSuQ==
@@ -2430,6 +2465,11 @@ jsesc@^2.5.1:
   resolved "https://registry.yarnpkg.com/jsesc/-/jsesc-2.5.2.tgz#80564d2e483dacf6e8ef209650a67df3f0c283a4"
   integrity sha512-OYu7XEzjkCQ3C5Ps3QIZsQfNpqoJyZZA99wd9aWd05NCtC5pWOkShK2mkL6HXQR6/Cy2lbNdPlZBpuQHXE63gA==
 
+jsesc@~0.5.0:
+  version "0.5.0"
+  resolved "https://registry.yarnpkg.com/jsesc/-/jsesc-0.5.0.tgz#e7dee66e35d6fc16f710fe91d5cf69f70f08911d"
+  integrity sha1-597mbjXW/Bb3EP6R1c9p9w8IkR0=
+
 json-parse-better-errors@^1.0.1:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/json-parse-better-errors/-/json-parse-better-errors-1.0.2.tgz#bb867cfb3450e69107c131d1c514bab3dc8bcaa9"
@@ -2552,6 +2592,13 @@ magic-string@^0.22.4:
   dependencies:
     vlq "^0.2.2"
 
+magic-string@^0.25.0, magic-string@^0.25.7:
+  version "0.25.7"
+  resolved "https://registry.yarnpkg.com/magic-string/-/magic-string-0.25.7.tgz#3f497d6fd34c669c6798dcb821f2ef31f5445051"
+  integrity sha512-4CrMT5DOHTDk4HYDlzmwu4FVCcIYI8gauveasrdCu2IKIFOJ3f0v/8MDGJCDL9oD2ppz/Av1b0Nj345H9M+XIA==
+  dependencies:
+    sourcemap-codec "^1.4.4"
+
 make-dir@^3.0.0:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/make-dir/-/make-dir-3.1.0.tgz#415e967046b3a7f1d185277d84aa58203726a13f"
@@ -3020,6 +3067,18 @@ readdirp@~3.4.0:
   dependencies:
     picomatch "^2.2.1"
 
+regenerate-unicode-properties@^8.0.2:
+  version "8.2.0"
+  resolved "https://registry.yarnpkg.com/regenerate-unicode-properties/-/regenerate-unicode-properties-8.2.0.tgz#e5de7111d655e7ba60c057dbe9ff37c87e65cdec"
+  integrity sha512-F9DjY1vKLo/tPePDycuH3dn9H1OTPIkVD9Kz4LODu+F2C75mgjAJ7x/gwy6ZcSNRAAkhNlJSOHRe8k3p+K9WhA==
+  dependencies:
+    regenerate "^1.4.0"
+
+regenerate@^1.4.0:
+  version "1.4.1"
+  resolved "https://registry.yarnpkg.com/regenerate/-/regenerate-1.4.1.tgz#cad92ad8e6b591773485fbe05a485caf4f457e6f"
+  integrity sha512-j2+C8+NtXQgEKWk49MMP5P/u2GhnahTtVkRIHr5R5lVRlbKvmQ+oS+A5aLKWp2ma5VkT8sh6v+v4hbH0YHR66A==
+
 regex-not@^1.0.0, regex-not@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/regex-not/-/regex-not-1.0.2.tgz#1f4ece27e00b0b65e0247a6810e6a85d83a5752c"
@@ -3028,6 +3087,30 @@ regex-not@^1.0.0, regex-not@^1.0.2:
     extend-shallow "^3.0.2"
     safe-regex "^1.1.0"
 
+regexpu-core@4.5.4:
+  version "4.5.4"
+  resolved "https://registry.yarnpkg.com/regexpu-core/-/regexpu-core-4.5.4.tgz#080d9d02289aa87fe1667a4f5136bc98a6aebaae"
+  integrity sha512-BtizvGtFQKGPUcTy56o3nk1bGRp4SZOTYrDtGNlqCQufptV5IkkLN6Emw+yunAJjzf+C9FQFtvq7IoA3+oMYHQ==
+  dependencies:
+    regenerate "^1.4.0"
+    regenerate-unicode-properties "^8.0.2"
+    regjsgen "^0.5.0"
+    regjsparser "^0.6.0"
+    unicode-match-property-ecmascript "^1.0.4"
+    unicode-match-property-value-ecmascript "^1.1.0"
+
+regjsgen@^0.5.0:
+  version "0.5.2"
+  resolved "https://registry.yarnpkg.com/regjsgen/-/regjsgen-0.5.2.tgz#92ff295fb1deecbf6ecdab2543d207e91aa33733"
+  integrity sha512-OFFT3MfrH90xIW8OOSyUrk6QHD5E9JOTeGodiJeBS3J6IwlgzJMNE/1bZklWz5oTg+9dCMyEetclvCVXOPoN3A==
+
+regjsparser@^0.6.0:
+  version "0.6.4"
+  resolved "https://registry.yarnpkg.com/regjsparser/-/regjsparser-0.6.4.tgz#a769f8684308401a66e9b529d2436ff4d0666272"
+  integrity sha512-64O87/dPDgfk8/RQqC4gkZoGyyWFIEUTTh80CU6CWuK5vkCGyekIx+oKcEIYtP/RAxSQltCZHCNu/mdd7fqlJw==
+  dependencies:
+    jsesc "~0.5.0"
+
 remove-trailing-separator@^1.0.1:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/remove-trailing-separator/-/remove-trailing-separator-1.1.0.tgz#c24bce2a283adad5bc3f58e0d48249b92379d8ef"
@@ -3344,6 +3427,11 @@ source-map@^0.7.3:
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.7.3.tgz#5302f8169031735226544092e64981f751750383"
   integrity sha512-CkCj6giN3S+n9qrYiBTX5gystlENnRW5jZeNLHpe6aue+SrHcG5VYwujhW9s4dY31mEGsxBDrHR6oI69fTXsaQ==
 
+sourcemap-codec@^1.4.4:
+  version "1.4.8"
+  resolved "https://registry.yarnpkg.com/sourcemap-codec/-/sourcemap-codec-1.4.8.tgz#ea804bd94857402e6992d05a38ef1ae35a9ab4c4"
+  integrity sha512-9NykojV5Uih4lgo5So5dtw+f0JgJX30KCNI8gwhz2J9A15wD0Ml6tjHKwf6fTSa6fAdVBdZeNOs9eJ71qCk8vA==
+
 spdx-correct@^3.0.0:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/spdx-correct/-/spdx-correct-3.1.0.tgz#fb83e504445268f154b074e218c87c003cd31df4"
@@ -3456,6 +3544,11 @@ strip-final-newline@^2.0.0:
   resolved "https://registry.yarnpkg.com/strip-final-newline/-/strip-final-newline-2.0.0.tgz#89b852fb2fcbe936f6f4b3187afb0a12c1ab58ad"
   integrity sha512-BrpvfNAE3dcvq7ll3xVumzjKjZQ5tI1sEUIKr3Uoks0XUl45St3FlatVqef9prk4jRDzhW6WZg+3bk93y6pLjA==
 
+strip-json-comments@^3.1.1:
+  version "3.1.1"
+  resolved "https://registry.yarnpkg.com/strip-json-comments/-/strip-json-comments-3.1.1.tgz#31f1281b3832630434831c310c01cccda8cbe006"
+  integrity sha512-6fPc+R4ihwqP6N/aIv2f1gMH8lOVtWQHoqC4yK6oSDVVocumAsfCqjkXnqiYMhmMwS/mEHLp7Vehlt3ql6lEig==
+
 sucrase@^3.15.0:
   version "3.15.0"
   resolved "https://registry.yarnpkg.com/sucrase/-/sucrase-3.15.0.tgz#78596a78be7264a65b52ed8d873883413ef0220c"
@@ -3683,6 +3776,29 @@ typescript@^3.9.7:
   resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.9.7.tgz#98d600a5ebdc38f40cb277522f12dc800e9e25fa"
   integrity sha512-BLbiRkiBzAwsjut4x/dsibSTB6yWpwT5qWmC2OfuCg3GgVQCSgMs4vEctYPhsaGtd0AeuuHMkjZ2h2WG8MSzRw==
 
+unicode-canonical-property-names-ecmascript@^1.0.4:
+  version "1.0.4"
+  resolved "https://registry.yarnpkg.com/unicode-canonical-property-names-ecmascript/-/unicode-canonical-property-names-ecmascript-1.0.4.tgz#2619800c4c825800efdd8343af7dd9933cbe2818"
+  integrity sha512-jDrNnXWHd4oHiTZnx/ZG7gtUTVp+gCcTTKr8L0HjlwphROEW3+Him+IpvC+xcJEFegapiMZyZe02CyuOnRmbnQ==
+
+unicode-match-property-ecmascript@^1.0.4:
+  version "1.0.4"
+  resolved "https://registry.yarnpkg.com/unicode-match-property-ecmascript/-/unicode-match-property-ecmascript-1.0.4.tgz#8ed2a32569961bce9227d09cd3ffbb8fed5f020c"
+  integrity sha512-L4Qoh15vTfntsn4P1zqnHulG0LdXgjSO035fEpdtp6YxXhMT51Q6vgM5lYdG/5X3MjS+k/Y9Xw4SFCY9IkR0rg==
+  dependencies:
+    unicode-canonical-property-names-ecmascript "^1.0.4"
+    unicode-property-aliases-ecmascript "^1.0.4"
+
+unicode-match-property-value-ecmascript@^1.1.0:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/unicode-match-property-value-ecmascript/-/unicode-match-property-value-ecmascript-1.2.0.tgz#0d91f600eeeb3096aa962b1d6fc88876e64ea531"
+  integrity sha512-wjuQHGQVofmSJv1uVISKLE5zO2rNGzM/KCYZch/QQvez7C1hUhBIuZ701fYXExuufJFMPhv2SyL8CyoIfMLbIQ==
+
+unicode-property-aliases-ecmascript@^1.0.4:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/unicode-property-aliases-ecmascript/-/unicode-property-aliases-ecmascript-1.1.0.tgz#dd57a99f6207bedff4628abefb94c50db941c8f4"
+  integrity sha512-PqSoPh/pWetQ2phoj5RLiaqIk4kCNwoV3CI+LfGmWLKI3rE3kl1h59XpX2BjgDrmbxD9ARtQobPGU1SguCYuQg==
+
 union-value@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/union-value/-/union-value-1.0.1.tgz#0b6fe7b835aecda61c6ea4d4f02c14221e109847"