diff --git a/biome.json b/biome.json
index ffad265675..a45844b6f2 100644
--- a/biome.json
+++ b/biome.json
@@ -15,7 +15,6 @@
       "complexity": {
         "noUselessSwitchCase": "off",
         "noUselessTernary": "off",
-        "useArrowFunction": "off",
         "useOptionalChain": "off"
       },
       "correctness": {
@@ -30,7 +29,6 @@
         "noGlobalEval": "off"
       },
       "style": {
-        "noArguments": "off",
         "noCommaOperator": "off",
         "noParameterAssign": "off",
         "noUselessElse": "off",
diff --git a/runtime/backtrace.js b/runtime/backtrace.js
index af63260989..4d922e7bad 100644
--- a/runtime/backtrace.js
+++ b/runtime/backtrace.js
@@ -19,7 +19,7 @@
 //Requires: jsoo_sys_getenv
 var caml_record_backtrace_env_flag = FLAG("with-js-error");
 
-(function () {
+(() => {
   var r = jsoo_sys_getenv("OCAMLRUNPARAM");
   if (r !== undefined) {
     var l = r.split(",");
diff --git a/runtime/blake2.js b/runtime/blake2.js
index ca17a471b0..5d07d2dcf0 100644
--- a/runtime/blake2.js
+++ b/runtime/blake2.js
@@ -1,6 +1,6 @@
 //Provides: blake2b
 //Version: >= 5.2
-var blake2b = (function () {
+var blake2b = (() => {
   // Blake2B in pure Javascript
   // Adapted from the reference implementation in RFC7693
   // Ported to Javascript by DC - https://github.com/dcposch
@@ -104,11 +104,7 @@ var blake2b = (function () {
   // These are offsets into a uint64 buffer.
   // Multiply them all by 2 to make them offsets into a uint32 buffer,
   // because this is Javascript and we don't have uint64s
-  const SIGMA82 = new Uint8Array(
-    SIGMA8.map(function (x) {
-      return x * 2;
-    }),
-  );
+  const SIGMA82 = new Uint8Array(SIGMA8.map((x) => x * 2));
 
   // Compression function. 'last' flag indicates last block.
   // Note we're representing 16 uint64s as 32 uint32s
diff --git a/runtime/effect.js b/runtime/effect.js
index d80a444932..0c9f33747f 100644
--- a/runtime/effect.js
+++ b/runtime/effect.js
@@ -60,7 +60,7 @@ function caml_push_trap(handler) {
 //If: effects
 function caml_pop_trap() {
   if (!caml_exn_stack)
-    return function (x) {
+    return (x) => {
       throw x;
     };
   var h = caml_exn_stack[1];
diff --git a/runtime/fs_fake.js b/runtime/fs_fake.js
index 1b88bc1496..3dea7de97b 100644
--- a/runtime/fs_fake.js
+++ b/runtime/fs_fake.js
@@ -42,9 +42,7 @@ MlFakeDevice.prototype.create_dir_if_needed = function (name) {
     this.content[res] = Symbol("directory");
   }
 };
-MlFakeDevice.prototype.slash = function (name) {
-  return /\/$/.test(name) ? name : name + "/";
-};
+MlFakeDevice.prototype.slash = (name) => (/\/$/.test(name) ? name : name + "/");
 MlFakeDevice.prototype.lookup = function (name) {
   if (!this.content[name] && this.lookupFun) {
     var res = this.lookupFun(
@@ -347,18 +345,14 @@ MlFakeFile.prototype.read = function (offset, buf, pos, len) {
 //Requires: caml_raise_sys_error
 function MlFakeFd_out(fd, flags) {
   MlFakeFile.call(this, caml_create_bytes(0));
-  this.log = function (s) {
-    return 0;
-  };
+  this.log = (s) => 0;
   if (fd == 1 && typeof console.log == "function") this.log = console.log;
   else if (fd == 2 && typeof console.error == "function")
     this.log = console.error;
   else if (typeof console.log == "function") this.log = console.log;
   this.flags = flags;
 }
-MlFakeFd_out.prototype.length = function () {
-  return 0;
-};
+MlFakeFd_out.prototype.length = () => 0;
 MlFakeFd_out.prototype.write = function (offset, buf, pos, len) {
   if (this.log) {
     if (
diff --git a/runtime/fs_node.js b/runtime/fs_node.js
index 8e6d6bf127..66461d630a 100644
--- a/runtime/fs_node.js
+++ b/runtime/fs_node.js
@@ -190,7 +190,7 @@ MlNodeDevice.prototype.opendir = function (name, raise_unix) {
     this.raise_nodejs_error(err, raise_unix);
   }
 };
-MlNodeDevice.prototype.raise_nodejs_error = function (err, raise_unix) {
+MlNodeDevice.prototype.raise_nodejs_error = (err, raise_unix) => {
   var unix_error = caml_named_value("Unix.Unix_error");
   if (raise_unix && unix_error) {
     var args = make_unix_err_args(err.code, err.syscall, err.path, err.errno);
@@ -199,7 +199,7 @@ MlNodeDevice.prototype.raise_nodejs_error = function (err, raise_unix) {
     caml_raise_sys_error(err.toString());
   }
 };
-MlNodeDevice.prototype.stats_from_js = function (js_stats) {
+MlNodeDevice.prototype.stats_from_js = (js_stats) => {
   /* ===Unix.file_kind===
    * type file_kind =
    *     S_REG                       (** Regular file *)
diff --git a/runtime/gc.js b/runtime/gc.js
index 8855240497..549ef88854 100644
--- a/runtime/gc.js
+++ b/runtime/gc.js
@@ -65,7 +65,7 @@ function caml_final_register() {
 var all_finalizers = new globalThis.Set();
 function caml_final_register_called_without_value(cb, a) {
   if (globalThis.FinalizationRegistry && a instanceof Object) {
-    var x = new globalThis.FinalizationRegistry(function (x) {
+    var x = new globalThis.FinalizationRegistry((x) => {
       all_finalizers.delete(x);
       cb(0);
       return;
diff --git a/runtime/graphics.js b/runtime/graphics.js
index 24c11e8ffb..c36512a685 100644
--- a/runtime/graphics.js
+++ b/runtime/graphics.js
@@ -76,7 +76,7 @@ function caml_gr_open_graph(info) {
   canvas.width = w;
   canvas.height = h;
   var ctx = caml_gr_state_create(canvas, w, h);
-  ctx.set_title = function (title) {
+  ctx.set_title = (title) => {
     doc.title = title;
   };
   caml_gr_state_set(ctx);
@@ -460,7 +460,7 @@ function caml_gr_draw_image(im, x, y) {
     canvas.height = s.height;
     canvas.getContext("2d").putImageData(im, 0, 0);
     var image = new globalThis.Image();
-    image.onload = function () {
+    image.onload = () => {
       s.context.drawImage(image, x, s.height - im.height - y);
       im.image = image;
     };
diff --git a/runtime/io.js b/runtime/io.js
index 2812b1bb96..6c56e3f5e7 100644
--- a/runtime/io.js
+++ b/runtime/io.js
@@ -94,7 +94,7 @@ function caml_sys_open(name, flags, _perms) {
   var file = root.device.open(root.rest, f);
   return caml_sys_open_internal(file, undefined);
 }
-(function () {
+(() => {
   function file(fd, flags) {
     if (fs_node_supported()) {
       return caml_sys_open_for_node(fd, flags);
@@ -284,7 +284,7 @@ function caml_ml_channel_size_64(chanid) {
 //Requires: caml_ml_channel_get
 function caml_ml_set_channel_output(chanid, f) {
   var chan = caml_ml_channel_get(chanid);
-  chan.output = function (s) {
+  chan.output = (s) => {
     f(s);
   };
   return 0;
diff --git a/runtime/jslib.js b/runtime/jslib.js
index 2d7887564f..8d215a55fe 100644
--- a/runtime/jslib.js
+++ b/runtime/jslib.js
@@ -111,9 +111,7 @@ function caml_callback(f, args) {
     };
     var res = {
       joo_tramp: f,
-      joo_args: args.concat(function (x) {
-        return x;
-      }),
+      joo_args: args.concat((x) => x),
     };
     do {
       caml_stack_depth = 40;
@@ -378,12 +376,8 @@ function caml_ojs_new_arr(c, a) {
 //Provides: caml_js_wrap_callback const (const)
 //Requires: caml_callback
 function caml_js_wrap_callback(f) {
-  return function () {
-    var len = arguments.length;
-    if (len > 0) {
-      var args = new Array(len);
-      for (var i = 0; i < len; i++) args[i] = arguments[i];
-    } else {
+  return (...args) => {
+    if (args.length <= 0) {
       args = [undefined];
     }
     var res = caml_callback(f, args);
@@ -394,76 +388,55 @@ function caml_js_wrap_callback(f) {
 //Provides: caml_js_wrap_callback_arguments
 //Requires: caml_callback
 function caml_js_wrap_callback_arguments(f) {
-  return function () {
-    var len = arguments.length;
-    var args = new Array(len);
-    for (var i = 0; i < len; i++) args[i] = arguments[i];
-    return caml_callback(f, [args]);
-  };
+  return (...args) => caml_callback(f, [args]);
 }
 //Provides: caml_js_wrap_callback_strict const
 //Requires: caml_callback
 function caml_js_wrap_callback_strict(arity, f) {
-  return function () {
-    var n = arguments.length;
-    var args = new Array(arity);
-    var len = Math.min(arguments.length, arity);
-    for (var i = 0; i < len; i++) args[i] = arguments[i];
+  return (...args) => {
+    args.length = arity;
     return caml_callback(f, args);
   };
 }
 //Provides: caml_js_wrap_callback_unsafe const (const)
 //Requires: caml_callback, caml_js_function_arity
 function caml_js_wrap_callback_unsafe(f) {
-  return function () {
+  return (...args) => {
     var len = caml_js_function_arity(f);
-    var args = new Array(len);
-    for (var i = 0; i < len; i++) args[i] = arguments[i];
+    args.length = len;
     return caml_callback(f, args);
   };
 }
 //Provides: caml_js_wrap_meth_callback const (const)
 //Requires: caml_callback, caml_js_wrap_callback
 function caml_js_wrap_meth_callback(f) {
-  return function () {
-    var len = arguments.length;
-    var args = new Array(len + 1);
-    args[0] = this;
-    for (var i = 0; i < len; i++) args[i + 1] = arguments[i];
-    var res = caml_callback(f, args);
+  return function (...args) {
+    const res = caml_callback(f, [this].concat(args));
     return res instanceof Function ? caml_js_wrap_callback(res) : res;
   };
 }
 //Provides: caml_js_wrap_meth_callback_arguments const (const)
 //Requires: caml_callback
 function caml_js_wrap_meth_callback_arguments(f) {
-  return function () {
-    var len = arguments.length;
-    var args = new Array(len);
-    for (var i = 0; i < len; i++) args[i] = arguments[i];
+  return function (...args) {
     return caml_callback(f, [this, args]);
   };
 }
 //Provides: caml_js_wrap_meth_callback_strict const
 //Requires: caml_callback
 function caml_js_wrap_meth_callback_strict(arity, f) {
-  return function () {
-    var args = new Array(arity + 1);
-    var len = Math.min(arguments.length, arity);
-    args[0] = this;
-    for (var i = 0; i < len; i++) args[i + 1] = arguments[i];
-    return caml_callback(f, args);
+  return function (...args) {
+    args.length = arity;
+    return caml_callback(f, [this].concat(args));
   };
 }
 //Provides: caml_js_wrap_meth_callback_unsafe const (const)
 //Requires: caml_callback, caml_js_function_arity
 function caml_js_wrap_meth_callback_unsafe(f) {
-  return function () {
-    var len = caml_js_function_arity(f) - 1;
-    var args = new Array(len + 1);
-    args[0] = this;
-    for (var i = 0; i < len; i++) args[i + 1] = arguments[i];
-    return caml_callback(f, args);
+  return function (...args) {
+    const len = caml_js_function_arity(f) - 1;
+    args.length = len;
+    return caml_callback(f, [this].concat(args));
   };
 }
 
diff --git a/runtime/marshal.js b/runtime/marshal.js
index f6eca871cc..17c956caf1 100644
--- a/runtime/marshal.js
+++ b/runtime/marshal.js
@@ -307,17 +307,13 @@ var caml_custom_ops = {
     fixed_length: 4,
   },
   _bigarray: {
-    deserialize: function (reader, sz) {
-      return caml_ba_deserialize(reader, sz, "_bigarray");
-    },
+    deserialize: (reader, sz) => caml_ba_deserialize(reader, sz, "_bigarray"),
     serialize: caml_ba_serialize,
     compare: caml_ba_compare,
     hash: caml_ba_hash,
   },
   _bigarr02: {
-    deserialize: function (reader, sz) {
-      return caml_ba_deserialize(reader, sz, "_bigarr02");
-    },
+    deserialize: (reader, sz) => caml_ba_deserialize(reader, sz, "_bigarr02"),
     serialize: caml_ba_serialize,
     compare: caml_ba_compare,
     hash: caml_ba_hash,
@@ -619,7 +615,7 @@ function caml_marshal_data_size(s, ofs) {
 //Provides: MlObjectTable
 var MlObjectTable;
 if (typeof globalThis.Map === "undefined") {
-  MlObjectTable = (function () {
+  MlObjectTable = (() => {
     /* polyfill (using linear search) */
     function NaiveLookup(objs) {
       this.objs = objs;
@@ -629,7 +625,7 @@ if (typeof globalThis.Map === "undefined") {
         if (this.objs[i] === v) return i;
       }
     };
-    NaiveLookup.prototype.set = function () {
+    NaiveLookup.prototype.set = () => {
       // Do nothing here. [MlObjectTable.store] will push to [this.objs] directly.
     };
 
@@ -664,7 +660,7 @@ MlObjectTable.prototype.recall = function (v) {
 //Requires: caml_is_ml_string, caml_ml_string_length, caml_string_unsafe_get
 //Requires: MlObjectTable, caml_list_to_js_array, caml_custom_ops
 //Requires: caml_invalid_argument,caml_string_of_jsbytes, caml_is_continuation_tag
-var caml_output_val = (function () {
+var caml_output_val = (() => {
   function Writer() {
     this.chunk = [];
   }
@@ -709,7 +705,7 @@ var caml_output_val = (function () {
       return this.chunk;
     },
   };
-  return function (v, flags) {
+  return (v, flags) => {
     flags = caml_list_to_js_array(flags);
 
     var no_sharing = flags.indexOf(0 /*Marshal.No_sharing*/) !== -1,
diff --git a/runtime/md5.js b/runtime/md5.js
index bf9a6f746c..d87d1793cf 100644
--- a/runtime/md5.js
+++ b/runtime/md5.js
@@ -53,7 +53,7 @@ function caml_md5_string(s, ofs, len) {
 }
 
 //Provides: caml_MD5Transform
-var caml_MD5Transform = (function () {
+var caml_MD5Transform = (() => {
   function add(x, y) {
     return (x + y) | 0;
   }
@@ -74,7 +74,7 @@ var caml_MD5Transform = (function () {
     return xx(c ^ (b | ~d), a, b, x, s, t);
   }
 
-  return function (w, buffer) {
+  return (w, buffer) => {
     var a = w[0],
       b = w[1],
       c = w[2],
diff --git a/runtime/stdlib.js b/runtime/stdlib.js
index d9e267df76..0c52c91c6e 100644
--- a/runtime/stdlib.js
+++ b/runtime/stdlib.js
@@ -32,7 +32,7 @@ function caml_call_gen(f, args) {
   } else {
     switch (d) {
       case 1: {
-        var g = function (x) {
+        var g = (x) => {
           var nargs = new Array(argsLen + 1);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
           nargs[argsLen] = x;
@@ -41,7 +41,7 @@ function caml_call_gen(f, args) {
         break;
       }
       case 2: {
-        var g = function (x, y) {
+        var g = (x, y) => {
           var nargs = new Array(argsLen + 2);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
           nargs[argsLen] = x;
@@ -51,12 +51,11 @@ function caml_call_gen(f, args) {
         break;
       }
       default: {
-        var g = function () {
-          var extra_args = arguments.length == 0 ? 1 : arguments.length;
-          var nargs = new Array(args.length + extra_args);
+        var g = (...extra_args) => {
+          var nargs = new Array(args.length + extra_args.length);
           for (var i = 0; i < args.length; i++) nargs[i] = args[i];
-          for (var i = 0; i < arguments.length; i++)
-            nargs[args.length + i] = arguments[i];
+          for (var i = 0; i < extra_args.length; i++)
+            nargs[args.length + i] = extra_args[i];
           return caml_call_gen(f, nargs);
         };
       }
@@ -79,7 +78,7 @@ function caml_call_gen(f, args) {
     var rest = args.slice(n - 1);
     var k = args[argsLen - 1];
     args = args.slice(0, n);
-    args[n - 1] = function (g) {
+    args[n - 1] = (g) => {
       if (typeof g !== "function") return k(g);
       var args = rest.slice();
       args[args.length - 1] = k;
@@ -91,7 +90,7 @@ function caml_call_gen(f, args) {
     var k = args[argsLen];
     switch (d) {
       case 1: {
-        var g = function (x, y) {
+        var g = (x, y) => {
           var nargs = new Array(argsLen + 2);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
           nargs[argsLen] = x;
@@ -101,7 +100,7 @@ function caml_call_gen(f, args) {
         break;
       }
       case 2: {
-        var g = function (x, y, z) {
+        var g = (x, y, z) => {
           var nargs = new Array(argsLen + 3);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
           nargs[argsLen] = x;
@@ -112,12 +111,11 @@ function caml_call_gen(f, args) {
         break;
       }
       default: {
-        var g = function () {
-          var extra_args = arguments.length == 0 ? 1 : arguments.length;
-          var nargs = new Array(argsLen + extra_args);
+        var g = (...extra_args) => {
+          var nargs = new Array(argsLen + extra_args.length);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
-          for (var i = 0; i < arguments.length; i++)
-            nargs[argsLen + i] = arguments[i];
+          for (var i = 0; i < extra_args.length; i++)
+            nargs[argsLen + i] = extra_args[i];
           return caml_call_gen(f, nargs);
         };
       }
diff --git a/runtime/stdlib_modern.js b/runtime/stdlib_modern.js
index f942292d4f..172fd945b3 100644
--- a/runtime/stdlib_modern.js
+++ b/runtime/stdlib_modern.js
@@ -30,7 +30,7 @@ function caml_call_gen(f, args) {
   } else {
     switch (d) {
       case 1: {
-        var g = function (x) {
+        var g = (x) => {
           var nargs = new Array(argsLen + 1);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
           nargs[argsLen] = x;
@@ -39,7 +39,7 @@ function caml_call_gen(f, args) {
         break;
       }
       case 2: {
-        var g = function (x, y) {
+        var g = (x, y) => {
           var nargs = new Array(argsLen + 2);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
           nargs[argsLen] = x;
@@ -49,12 +49,11 @@ function caml_call_gen(f, args) {
         break;
       }
       default: {
-        var g = function () {
-          var extra_args = arguments.length == 0 ? 1 : arguments.length;
-          var nargs = new Array(args.length + extra_args);
+        var g = (...extra_args) => {
+          var nargs = new Array(args.length + extra_args.length);
           for (var i = 0; i < args.length; i++) nargs[i] = args[i];
-          for (var i = 0; i < arguments.length; i++)
-            nargs[args.length + i] = arguments[i];
+          for (var i = 0; i < extra_args.length; i++)
+            nargs[args.length + i] = extra_args[i];
           return caml_call_gen(f, nargs);
         };
       }
@@ -75,7 +74,7 @@ function caml_call_gen(f, args) {
     var rest = args.slice(n - 1);
     var k = args[argsLen - 1];
     args = args.slice(0, n);
-    args[n - 1] = function (g) {
+    args[n - 1] = (g) => {
       if (typeof g !== "function") return k(g);
       var args = rest.slice();
       args[args.length - 1] = k;
@@ -87,7 +86,7 @@ function caml_call_gen(f, args) {
     var k = args[argsLen];
     switch (d) {
       case 1: {
-        var g = function (x, y) {
+        var g = (x, y) => {
           var nargs = new Array(argsLen + 2);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
           nargs[argsLen] = x;
@@ -97,7 +96,7 @@ function caml_call_gen(f, args) {
         break;
       }
       case 2: {
-        var g = function (x, y, z) {
+        var g = (x, y, z) => {
           var nargs = new Array(argsLen + 3);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
           nargs[argsLen] = x;
@@ -108,12 +107,11 @@ function caml_call_gen(f, args) {
         break;
       }
       default: {
-        var g = function () {
-          var extra_args = arguments.length == 0 ? 1 : arguments.length;
-          var nargs = new Array(argsLen + extra_args);
+        var g = (...extra_args) => {
+          var nargs = new Array(argsLen + extra_args.length);
           for (var i = 0; i < argsLen; i++) nargs[i] = args[i];
-          for (var i = 0; i < arguments.length; i++)
-            nargs[argsLen + i] = arguments[i];
+          for (var i = 0; i < extra_args.length; i++)
+            nargs[argsLen + i] = extra_args[i];
           return caml_call_gen(f, nargs);
         };
       }
diff --git a/runtime/str.js b/runtime/str.js
index a58190b805..5578d0cae2 100644
--- a/runtime/str.js
+++ b/runtime/str.js
@@ -24,7 +24,7 @@
 //Requires: caml_jsbytes_of_string, caml_js_from_array, caml_uint8_array_of_string
 //Requires: caml_string_get
 
-var re_match = (function () {
+var re_match = (() => {
   var re_word_letters = [
     0x00, 0x00, 0x00, 0x00 /* 0x00-0x1F: none */, 0x00, 0x00, 0xff,
     0x03 /* 0x20-0x3F: digits 0-9 */, 0xfe, 0xff, 0xff,
@@ -86,7 +86,7 @@ var re_match = (function () {
     }
     groups[0].start = pos;
 
-    var backtrack = function () {
+    var backtrack = () => {
       while (stack.length) {
         var item = stack.pop();
         if (item.undo) {
@@ -100,11 +100,11 @@ var re_match = (function () {
       quit = true;
     };
 
-    var push = function (item) {
+    var push = (item) => {
       stack.push(item);
     };
 
-    var accept = function () {
+    var accept = () => {
       groups[0].end = pos;
       var result = new Array(1 + groups.length * 2);
       result[0] = 0; // tag
@@ -119,7 +119,7 @@ var re_match = (function () {
       return result;
     };
 
-    var prefix_match = function () {
+    var prefix_match = () => {
       if (partial) return accept();
       else backtrack();
     };
diff --git a/runtime/sys.js b/runtime/sys.js
index 9e596f1781..8527359962 100644
--- a/runtime/sys.js
+++ b/runtime/sys.js
@@ -134,7 +134,7 @@ function caml_sys_unsafe_getenv(name) {
 
 //Provides: caml_argv
 //Requires: caml_string_of_jsstring
-var caml_argv = (function () {
+var caml_argv = (() => {
   var process = globalThis.process;
   var main = "a.out";
   var args = [];
@@ -369,12 +369,12 @@ function caml_sys_is_regular_file(name) {
 function caml_setup_uncaught_exception_handler() {
   var process = globalThis.process;
   if (process && process.on) {
-    process.on("uncaughtException", function (err, origin) {
+    process.on("uncaughtException", (err, origin) => {
       caml_fatal_uncaught_exception(err);
       process.exit(2);
     });
   } else if (globalThis.addEventListener) {
-    globalThis.addEventListener("error", function (event) {
+    globalThis.addEventListener("error", (event) => {
       if (event.error) {
         caml_fatal_uncaught_exception(event.error);
       }
diff --git a/runtime/weak.js b/runtime/weak.js
index ad5769abd4..a238a24106 100644
--- a/runtime/weak.js
+++ b/runtime/weak.js
@@ -169,7 +169,7 @@ function caml_ephe_get_data_copy(x) {
 function caml_ephe_set_data(x, data) {
   if (globalThis.FinalizationRegistry && globalThis.WeakRef) {
     if (!(x[1] instanceof globalThis.FinalizationRegistry)) {
-      x[1] = new globalThis.FinalizationRegistry(function () {
+      x[1] = new globalThis.FinalizationRegistry(() => {
         caml_ephe_unset_data(x);
       });
       //register all keys
diff --git a/runtime/zstd.js b/runtime/zstd.js
index 01da0cad12..21bc73c2de 100644
--- a/runtime/zstd.js
+++ b/runtime/zstd.js
@@ -1,6 +1,6 @@
 //Provides: zstd_decompress
 //Version: >= 5.1
-var zstd_decompress = (function () {
+var zstd_decompress = (() => {
   // aliases for shorter compressed code (most minifers don't do this)
   var ab = ArrayBuffer,
     u8 = Uint8Array,
@@ -8,7 +8,7 @@ var zstd_decompress = (function () {
     i16 = Int16Array,
     u32 = Uint32Array,
     i32 = Int32Array;
-  var slc = function (v, s, e) {
+  var slc = (v, s, e) => {
     if (u8.prototype.slice) return u8.prototype.slice.call(v, s, e);
     if (s == null || s < 0) s = 0;
     if (e == null || e > v.length) e = v.length;
@@ -16,14 +16,14 @@ var zstd_decompress = (function () {
     n.set(v.subarray(s, e));
     return n;
   };
-  var fill = function (v, n, s, e) {
+  var fill = (v, n, s, e) => {
     if (u8.prototype.fill) return u8.prototype.fill.call(v, n, s, e);
     if (s == null || s < 0) s = 0;
     if (e == null || e > v.length) e = v.length;
     for (; s < e; ++s) v[s] = n;
     return v;
   };
-  var cpw = function (v, t, s, e) {
+  var cpw = (v, t, s, e) => {
     if (u8.prototype.copyWithin)
       return u8.prototype.copyWithin.call(v, t, s, e);
     if (s == null || s < 0) s = 0;
@@ -44,23 +44,22 @@ var zstd_decompress = (function () {
     "match distance too far back",
     "unexpected EOF",
   ];
-  var err = function (ind, msg, nt) {
+  var err = (ind, msg, nt) => {
     var e = new Error(msg || ec[ind]);
     e.code = ind;
     if (!nt) throw e;
     return e;
   };
-  var rb = function (d, b, n) {
+  var rb = (d, b, n) => {
     var i = 0,
       o = 0;
     for (; i < n; ++i) o |= d[b++] << (i << 3);
     return o;
   };
-  var b4 = function (d, b) {
-    return (d[b] | (d[b + 1] << 8) | (d[b + 2] << 16) | (d[b + 3] << 24)) >>> 0;
-  };
+  var b4 = (d, b) =>
+    (d[b] | (d[b + 1] << 8) | (d[b + 2] << 16) | (d[b + 3] << 24)) >>> 0;
   // read Zstandard frame header
-  var rzfh = function (dat, w) {
+  var rzfh = (dat, w) => {
     var n3 = dat[0] | (dat[1] << 8) | (dat[2] << 16);
     if (n3 == 0x2fb528 && dat[3] == 253) {
       // Zstandard
@@ -111,13 +110,13 @@ var zstd_decompress = (function () {
     err(0);
   };
   // most significant bit for nonzero
-  var msb = function (val) {
+  var msb = (val) => {
     var bits = 0;
     for (; 1 << bits <= val; ++bits);
     return bits - 1;
   };
   // read finite state entropy
-  var rfse = function (dat, bt, mal) {
+  var rfse = (dat, bt, mal) => {
     // table pos
     var tpos = (bt << 3) + 4;
     // accuracy log
@@ -215,7 +214,7 @@ var zstd_decompress = (function () {
     ];
   };
   // read huffman
-  var rhu = function (dat, bt) {
+  var rhu = (dat, bt) => {
     //  index  weight count
     var i = 0,
       wc = -1;
@@ -350,7 +349,7 @@ var zstd_decompress = (function () {
     5,
   )[1];
   // bits to baseline
-  var b2bl = function (b, s) {
+  var b2bl = (b, s) => {
     var len = b.length,
       bl = new i32(len);
     for (var i = 0; i < len; ++i) {
@@ -381,7 +380,7 @@ var zstd_decompress = (function () {
   // match length baseline
   var mlbl = /*#__PURE__ */ b2bl(mlb, 3);
   // decode huffman stream
-  var dhu = function (dat, out, hu) {
+  var dhu = (dat, out, hu) => {
     var len = dat.length,
       ss = out.length,
       lb = dat[len - 1],
@@ -404,7 +403,7 @@ var zstd_decompress = (function () {
   };
   // decode huffman stream 4x
   // TODO: use workers to parallelize
-  var dhu4 = function (dat, out, hu) {
+  var dhu4 = (dat, out, hu) => {
     var bt = 6;
     var ss = out.length,
       sz1 = (ss + 3) >> 2,
@@ -428,7 +427,7 @@ var zstd_decompress = (function () {
     dhu(dat.subarray(bt), out.subarray(sz3), hu);
   };
   // read Zstandard block
-  var rzb = function (dat, st, out) {
+  var rzb = (dat, st, out) => {
     var _a;
     var bt = st.b;
     //    byte 0        block type
@@ -643,7 +642,7 @@ var zstd_decompress = (function () {
     err(2);
   };
   // concat
-  var cct = function (bufs, ol) {
+  var cct = (bufs, ol) => {
     if (bufs.length == 1) return bufs[0];
     var buf = new u8(ol);
     for (var i = 0, b = 0; i < bufs.length; ++i) {