diff --git a/fluent-bundle/makefile b/fluent-bundle/makefile
index c7210775a..2ed518018 100644
--- a/fluent-bundle/makefile
+++ b/fluent-bundle/makefile
@@ -51,7 +51,7 @@ html:
 	    --excludePrivate \
 	    --logger none \
 	    --hideGenerator
-	@echo -e " $(OK) html build"
+	@echo -e " $(OK) html built"
 
 clean:
 	@rm -f esm/*.js esm/*.d.ts esm/.compiled
diff --git a/fluent-dedent/.esdoc.json b/fluent-dedent/.esdoc.json
deleted file mode 100644
index 9f61dff1a..000000000
--- a/fluent-dedent/.esdoc.json
+++ /dev/null
@@ -1,16 +0,0 @@
-{
-    "source": "./src",
-    "destination": "../html/dedent",
-    "plugins": [
-        {
-            "name": "esdoc-standard-plugin"
-        },
-        {
-            "name": "esdoc-ecmascript-proposal-plugin",
-            "option": {
-                "objectRestSpread": true,
-                "asyncGenerators": true
-            }
-        }
-    ]
-}
diff --git a/fluent-dedent/.gitignore b/fluent-dedent/.gitignore
index 7d147bec1..99472bc4d 100644
--- a/fluent-dedent/.gitignore
+++ b/fluent-dedent/.gitignore
@@ -1,2 +1,3 @@
+esm/
 /index.js
 /compat.js
diff --git a/fluent-dedent/.npmignore b/fluent-dedent/.npmignore
index f520b36f5..abad613ff 100644
--- a/fluent-dedent/.npmignore
+++ b/fluent-dedent/.npmignore
@@ -1,5 +1,7 @@
 .nyc_output
 coverage
-docs
+esm/.compiled
+src
 test
 makefile
+tsconfig.json
diff --git a/fluent-dedent/makefile b/fluent-dedent/makefile
index c6585be16..dd474ba50 100644
--- a/fluent-dedent/makefile
+++ b/fluent-dedent/makefile
@@ -3,16 +3,30 @@ GLOBAL  := FluentDedent
 
 include ../common.mk
 
-build: index.js compat.js
+lint:
+	@eslint --config $(ROOT)/eslint_ts.json --max-warnings 0 src/*.ts
+	@eslint --config $(ROOT)/eslint_test.json --max-warnings 0 test/
+	@echo -e " $(OK) lint"
+
+.PHONY: compile
+compile: esm/.compiled
+
+esm/.compiled: $(SOURCES)
+	@tsc
+	@touch $@
+	@echo -e " $(OK) esm/ compiled"
 
-test:
+.PHONY: test
+test: esm/.compiled
 	@nyc --reporter=text --reporter=html mocha \
 	    --recursive --ui tdd \
 	    --require esm \
 	    test/**/*_test.js
 
-index.js: $(SOURCES)
-	@rollup $(CURDIR)/src/index.js \
+build: index.js compat.js
+
+index.js: esm/.compiled
+	@rollup $(CURDIR)/esm/index.js \
 	    --config $(ROOT)/bundle_config.js \
 	    --banner "/* $(PACKAGE)@$(VERSION) */" \
 	    --amd.id $(PACKAGE) \
@@ -20,8 +34,8 @@ index.js: $(SOURCES)
 	    --output.file $@
 	@echo -e " $(OK) $@ built"
 
-compat.js: $(SOURCES)
-	@rollup $(CURDIR)/src/index.js \
+compat.js: esm/.compiled
+	@rollup $(CURDIR)/esm/index.js \
 	    --config $(ROOT)/compat_config.js \
 	    --banner "/* $(PACKAGE)@$(VERSION) */" \
 	    --amd.id $(PACKAGE) \
@@ -29,6 +43,18 @@ compat.js: $(SOURCES)
 	    --output.file $@
 	@echo -e " $(OK) $@ built"
 
-lint: _lint
-html: _html
-clean: _clean
+html:
+	@typedoc src \
+	    --out ../html/dedent \
+	    --mode file \
+	    --excludeNotExported \
+	    --excludePrivate \
+	    --logger none \
+	    --hideGenerator
+	@echo -e " $(OK) html built"
+
+clean:
+	@rm -f esm/*.js esm/*.d.ts esm/.compiled
+	@rm -f index.js compat.js
+	@rm -rf .nyc_output coverage
+	@echo -e " $(OK) clean"
diff --git a/fluent-dedent/package.json b/fluent-dedent/package.json
index 0c9ddd263..8c493f5aa 100644
--- a/fluent-dedent/package.json
+++ b/fluent-dedent/package.json
@@ -11,11 +11,10 @@
       "email": "stas@mozilla.com"
     }
   ],
-  "directories": {
-    "lib": "./src"
-  },
+  "type": "commonjs",
   "main": "./index.js",
-  "module": "./src/index.js",
+  "module": "./esm/index.js",
+  "types": "./esm/index.d.ts",
   "repository": {
     "type": "git",
     "url": "https://github.com/projectfluent/fluent.js.git"
diff --git a/fluent-dedent/src/index.js b/fluent-dedent/src/index.ts
similarity index 68%
rename from fluent-dedent/src/index.js
rename to fluent-dedent/src/index.ts
index 7079f7119..f7fc61af6 100644
--- a/fluent-dedent/src/index.js
+++ b/fluent-dedent/src/index.ts
@@ -9,37 +9,46 @@ const RE_BLANK = /^[ \t]*$/;
  * line and it must end on a line of its own, with the closing delimiter on a
  * next line.
  *
- * @param {Array<string>} strings
- * @param {...any} values
- * @returns string
+ * @param strings
+ * @param values
  */
-export default function ftl(strings, ...values) {
+export default function ftl(
+  strings: TemplateStringsArray,
+  ...values: Array<unknown>
+): string {
   let code = strings.reduce((acc, cur) => acc + values.shift() + cur);
   let lines = code.split("\n");
-  let [first, commonIndent] = [lines.shift(), lines.pop()];
 
-  if (!RE_BLANK.test(first)) {
+  let first = lines.shift();
+  if (first === undefined || !RE_BLANK.test(first)) {
     throw new RangeError("Content must start on a new line.");
   }
-  if (!RE_BLANK.test(commonIndent)) {
+
+  let commonIndent = lines.pop();
+  if (commonIndent === undefined || !RE_BLANK.test(commonIndent)) {
     throw new RangeError("Closing delimiter must appear on a new line.");
   }
 
-  function dedent(line, idx) {
+  let dedented = [];
+  for (let i = 0; i < lines.length; i++) {
+    let line = lines[i];
     let lineIndent = line.slice(0, commonIndent.length);
     if (lineIndent.length === 0) {
       // Empty blank lines are preserved even if technically they are not
       // indented at all. This also short-circuits the dedentation logic when
       // commonIndent.length is 0, i.e. when all indents should be kept.
-      return line;
+      dedented.push(line);
+      continue;
     }
+
     if (lineIndent !== commonIndent) {
       // The indentation of the line must match commonIndent exacty.
-      throw new RangeError(`Insufficient indentation in line ${idx + 1}.`);
+      throw new RangeError(`Insufficient indentation in line ${i + 1}.`);
     }
+
     // Strip commonIndent.
-    return line.slice(commonIndent.length);
+    dedented.push(line.slice(commonIndent.length));
   }
 
-  return lines.map(dedent).join("\n");
+  return dedented.join("\n");
 }
diff --git a/fluent-dedent/test/blank_test.js b/fluent-dedent/test/blank_test.js
index 08a203e49..31e20013e 100644
--- a/fluent-dedent/test/blank_test.js
+++ b/fluent-dedent/test/blank_test.js
@@ -1,7 +1,7 @@
 "use strict";
 
 import assert from "assert";
-import ftl from "../src/index";
+import ftl from "../esm/index";
 
 suite("blank lines", function() {
   test("leading", function() {
diff --git a/fluent-dedent/test/content_test.js b/fluent-dedent/test/content_test.js
index d94eaa461..df2037273 100644
--- a/fluent-dedent/test/content_test.js
+++ b/fluent-dedent/test/content_test.js
@@ -1,7 +1,7 @@
 "use strict";
 
 import assert from "assert";
-import ftl from "../src/index";
+import ftl from "../esm/index";
 
 suite("content lines", function() {
   test("no indent", function () {
diff --git a/fluent-dedent/test/eol_test.js b/fluent-dedent/test/eol_test.js
index 14d886b7e..6b3896c9b 100644
--- a/fluent-dedent/test/eol_test.js
+++ b/fluent-dedent/test/eol_test.js
@@ -1,7 +1,7 @@
 "use strict";
 
 import assert from "assert";
-import ftl from "../src/index";
+import ftl from "../esm/index";
 
 suite("EOL at extremes", function () {
   test("no EOLs", function () {
diff --git a/fluent-dedent/test/interpolation_test.js b/fluent-dedent/test/interpolation_test.js
index 45a495d37..0039911ce 100644
--- a/fluent-dedent/test/interpolation_test.js
+++ b/fluent-dedent/test/interpolation_test.js
@@ -1,7 +1,7 @@
 "use strict";
 
 import assert from "assert";
-import ftl from "../src/index";
+import ftl from "../esm/index";
 
 suite("interpolation", function() {
   test("single", function() {
diff --git a/fluent-dedent/test/mixed_test.js b/fluent-dedent/test/mixed_test.js
index 340b4fe4d..259c36ab0 100644
--- a/fluent-dedent/test/mixed_test.js
+++ b/fluent-dedent/test/mixed_test.js
@@ -1,7 +1,7 @@
 "use strict";
 
 import assert from "assert";
-import ftl from "../src/index";
+import ftl from "../esm/index";
 
 suite("mixed indent", function() {
   test("same amount", function() {
diff --git a/fluent-dedent/test/tabs_test.js b/fluent-dedent/test/tabs_test.js
index 87f07e60b..4246871ef 100644
--- a/fluent-dedent/test/tabs_test.js
+++ b/fluent-dedent/test/tabs_test.js
@@ -1,7 +1,7 @@
 "use strict";
 
 import assert from "assert";
-import ftl from "../src/index";
+import ftl from "../esm/index";
 
 suite("tab indent", function() {
   test("same amount", function() {
diff --git a/fluent-dedent/tsconfig.json b/fluent-dedent/tsconfig.json
new file mode 100644
index 000000000..45fefaee8
--- /dev/null
+++ b/fluent-dedent/tsconfig.json
@@ -0,0 +1,16 @@
+{
+    "compilerOptions": {
+        "target": "es2019",
+        "module": "es2015",
+        "strict": true,
+        "allowJs": false,
+        "esModuleInterop": true,
+        "moduleResolution": "node",
+        "noEmitHelpers": true,
+        "declaration": true,
+        "outDir": "./esm",
+    },
+    "include": [
+        "./src/**/*.ts"
+    ]
+}
diff --git a/fluent-sequence/makefile b/fluent-sequence/makefile
index b7db9dc3b..0a255aa0f 100644
--- a/fluent-sequence/makefile
+++ b/fluent-sequence/makefile
@@ -25,7 +25,7 @@ test: esm/.compiled
 
 build: index.js compat.js
 
-index.js: $(SOURCES)
+index.js: esm/.compiled
 	@rollup $(CURDIR)/esm/index.js \
 	    --config $(ROOT)/bundle_config.js \
 	    --banner "/* $(PACKAGE)@$(VERSION) */" \
@@ -34,7 +34,7 @@ index.js: $(SOURCES)
 	    --output.file $@
 	@echo -e " $(OK) $@ built"
 
-compat.js: $(SOURCES)
+compat.js: esm/.compiled
 	@rollup $(CURDIR)/esm/index.js \
 	    --config $(ROOT)/compat_config.js \
 	    --banner "/* $(PACKAGE)@$(VERSION) */" \
@@ -45,13 +45,13 @@ compat.js: $(SOURCES)
 
 html:
 	@typedoc src \
-	    --out ../html/bundle \
+	    --out ../html/sequence \
 	    --mode file \
 	    --excludeNotExported \
 	    --excludePrivate \
 	    --logger none \
 	    --hideGenerator
-	@echo -e " $(OK) html build"
+	@echo -e " $(OK) html built"
 
 clean:
 	@rm -f esm/*.js esm/*.d.ts esm/.compiled