perf: reduce size

Author: TomerAberbach

readme.md

@@ -30,7 +30,7 @@
 - **Robust:** Works
   [cross-realm](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/instanceof#instanceof_and_multiple_realms)
 - **Secure:** Resilient to spoofing
-- **Tiny:** One 0.93 kB gzipped package instead of
+- **Tiny:** One 0.89 kB gzipped package instead of
   [`which-builtin-type`'s 10.5 kB gzipped total size](https://bundlejs.com/?q=which-builtin-type%401.2.1)
   with [50 dependencies](https://npmgraph.js.org/?q=which-builtin-type#zoom=w)
 

src/index.ts

@@ -102,10 +102,7 @@ const builtinType = (value: unknown): BuiltinType => {
   }
 }
 
-const INTERNAL_SLOT_STATIC_NAMES: [BuiltinType, string][] = [
-  [`Array`, `isArray`],
-  [`Buffer`, `isBuffer`],
-]
+const INTERNAL_SLOT_PREDICATE_NAMES: BuiltinType[] = [`Array`, `Buffer`]
 const INTERNAL_SLOT_PROTOTYPE_NAMES: [BuiltinType, string, any[]?][] = [
   [`Boolean`, `valueOf`],
   [`Number`, `valueOf`],
@@ -135,7 +132,7 @@ const INTERNAL_SLOT_PROTOTYPE_NAMES: [BuiltinType, string, any[]?][] = [
   [`Temporal.PlainMonthDay`, `monthCode`],
   [`Temporal.Duration`, `sign`],
 ]
-const BUILTIN_ERROR_SUBCLASS_NAMES = new Set<string>([
+const BUILTIN_ERROR_SUBCLASS_NAMES = new Set<string | undefined>([
   `EvalError`,
   `RangeError`,
   `ReferenceError`,
@@ -145,18 +142,16 @@ const BUILTIN_ERROR_SUBCLASS_NAMES = new Set<string>([
   `AggregateError`,
 ])
 
-type BuiltinTypeFunction = (value: object) => BuiltinType | undefined
+type BuiltinTypeFunction = (value: object) => BuiltinType | `` | undefined
 
 const TYPE_TAG_FUNCTIONS: BuiltinTypeFunction[] = [
-  ...INTERNAL_SLOT_STATIC_NAMES.flatMap<BuiltinTypeFunction>(([type, name]) => {
-    const Class = globalThis[type as keyof typeof globalThis] as
-      | Record<string, (value: unknown) => boolean>
-      | undefined
-    if (!Class) {
-      return []
-    }
-    const func = Class[name]!
-    return value => (func(value) ? type : undefined)
+  ...INTERNAL_SLOT_PREDICATE_NAMES.flatMap<BuiltinTypeFunction>(type => {
+    const func = (
+      globalThis[type as keyof typeof globalThis] as
+        | Record<string, (value: unknown) => boolean>
+        | undefined
+    )?.[`is${type}`]
+    return func ? value => (func(value) ? type : ``) : []
   }),
   ...INTERNAL_SLOT_PROTOTYPE_NAMES.flatMap<BuiltinTypeFunction>(
     ([type, name, args = []]) => {
@@ -173,13 +168,14 @@ const TYPE_TAG_FUNCTIONS: BuiltinTypeFunction[] = [
         return []
       }
       let descriptor: PropertyDescriptor | undefined
-      do {
-        descriptor = Object.getOwnPropertyDescriptor(prototype, name)
-        if (descriptor) {
-          break
-        }
+      for (
+        ;
+        prototype &&
+        !(descriptor = Object.getOwnPropertyDescriptor(prototype, name));
         prototype = Object.getPrototypeOf(prototype) as object | null
-      } while (prototype)
+      ) {
+        //
+      }
       if (!descriptor) {
         return []
       }
@@ -192,9 +188,9 @@ const TYPE_TAG_FUNCTIONS: BuiltinTypeFunction[] = [
         // Each function above will do one of the following when applied to a
         // value not of the proper type:
         // 1. Throw
-        // 2. Return `null` or `undefined
+        // 2. Return `null` or `undefined`
         try {
-          return func.apply(value, args) == null ? undefined : type
+          return func.apply(value, args) == null ? `` : type
         } catch {
           return undefined
         }
@@ -203,7 +199,7 @@ const TYPE_TAG_FUNCTIONS: BuiltinTypeFunction[] = [
   ),
 ]
 const typedArrayToStringTag = Object.getOwnPropertyDescriptor(
-  Object.getPrototypeOf(Uint8Array.prototype),
+  Object.getPrototypeOf(Int8Array.prototype),
   Symbol.toStringTag,
 )?.get
 if (typedArrayToStringTag) {
@@ -212,26 +208,21 @@ if (typedArrayToStringTag) {
   )
 }
 TYPE_TAG_FUNCTIONS.push(value => {
-  // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
-  if (!(Error.isError?.(value) ?? toStringType(value) == `Error`)) {
-    return undefined
+  const type =
+    !(Symbol.toStringTag in value) &&
+    Object.prototype.toString.call(value).slice(8, -1)
+  if (type == `Arguments`) {
+    return type
   }
-  const prototype = Object.getPrototypeOf(value) as { name?: string } | null
-  if (prototype === null) {
-    return `Error`
+  // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+  if (Error.isError?.(value) ?? type == `Error`) {
+    const name = (Object.getPrototypeOf(value) as { name?: string } | null)
+      ?.name
+    return BUILTIN_ERROR_SUBCLASS_NAMES.has(name)
+      ? (name as BuiltinType)
+      : `Error`
   }
-  return BUILTIN_ERROR_SUBCLASS_NAMES.has(prototype.name!)
-    ? (prototype.name as BuiltinType)
-    : `Error`
+  return undefined
 })
-TYPE_TAG_FUNCTIONS.push(value => {
-  const type = toStringType(value)
-  return type == `Arguments` ? type : undefined
-})
-
-const toStringType = (value: object) =>
-  Object.hasOwn(value, Symbol.toStringTag)
-    ? ``
-    : Object.prototype.toString.call(value).slice(8, -1)
 
 export default builtinType