Lady’s Gitweb - Pisces/blob - function.js

   1 // ♓🌟 Piscēs ∷ function.js
   2 // ====================================================================
   3 //
   4 // Copyright © 2022 Lady [@ Lady’s Computer].
   5 //
   6 // This Source Code Form is subject to the terms of the Mozilla Public
   7 // License, v. 2.0. If a copy of the MPL was not distributed with this
   8 // file, You can obtain one at <https://mozilla.org/MPL/2.0/>.
   9
  10 export const {
  11   /**
  12    * Creates a bound function from the provided function using the
  13    * provided this value and arguments list.
  14    *
  15    * ☡ As with call and construct, the arguments must be passed as an
  16    * array.
  17    */
  18   bind,
  19
  20   /**
  21    * Returns a new function which calls the provided function with its
  22    * first argument as the `this` value and the remaining arguments
  23    * passed through.
  24    *
  25    * ※ This is effectively an alias for Function.prototype.call.bind.
  26    */
  27   makeCallable,
  28 } = (() => {
  29   // ☡ Because these functions are used to initialize module constants,
  30   // they can’t depend on imports from elsewhere.
  31   const {
  32     bind: functionBind,
  33     call: functionCall,
  34   } = Function.prototype;
  35   const callBind = Reflect.apply(functionBind, functionCall, [
  36     functionBind,
  37   ]);
  38   const {
  39     create: objectCreate,
  40     defineProperty: defineOwnProperty,
  41     getPrototypeOf: getPrototype,
  42   } = Object;
  43   const { iterator: iteratorSymbol } = Symbol;
  44   const { [iteratorSymbol]: arrayIterator } = Array.prototype;
  45   const {
  46     next: arrayIteratorNext,
  47   } = getPrototype([][iteratorSymbol]());
  48   const argumentIterablePrototype = {
  49     [iteratorSymbol]() {
  50       return {
  51         next: callBind(
  52           arrayIteratorNext,
  53           call(arrayIterator, this.args, []),
  54         ),
  55       };
  56     },
  57   };
  58   return {
  59     bind: ($, boundThis, boundArgs) =>
  60       callBind(
  61         $,
  62         boundThis,
  63         ...objectCreate(
  64           argumentIterablePrototype,
  65           { args: { value: boundArgs } },
  66         ),
  67       ),
  68     makeCallable: ($) =>
  69       defineOwnProperty(
  70         callBind(functionCall, $),
  71         "length",
  72         { value: $.length + 1 },
  73       ),
  74   };
  75 })();
  76
  77 /**
  78  * Calls the provided function with the provided this value and
  79  * arguments list.
  80  *
  81  * ☡ This is an alias for Reflect.apply—the arguments must be passed
  82  * as an array.
  83  */
  84 export const call = Reflect.apply;
  85
  86 /**
  87  * Constructs the provided function with the provided arguments list
  88  * and new target.
  89  *
  90  * ☡ This is an alias for Reflect.construct—the arguments must be
  91  * passed as an array.
  92  */
  93 export const construct = Reflect.construct;
  94
  95 /**
  96  * Returns the provided value.
  97  *
  98  * ※ This function can be called as a constructor. When used in an
  99  * `extends` clause and called via `super`, it will set the value of
 100  * `this` to the provided value, enabling it to be extended with
 101  * private class features.
 102  */
 103 export const identity = function ($) {
 104   return $;
 105 };
 106
 107 /** Returns whether the provided value is callable. */
 108 export const isCallable = ($) => typeof $ === "function";
 109
 110 /** Returns whether the provided value is a constructor. */
 111 export const isConstructor = ($) => {
 112   // The provided value is an object.
 113   try {
 114     construct(
 115       function () {},
 116       [],
 117       $,
 118     ); // will throw if $ is not a constructor
 119     return true;
 120   } catch {
 121     return false;
 122   }
 123 };
 124
 125 /**
 126  * Returns whether the provided object inherits from the prototype of
 127  * the provided function.
 128  */
 129 export const ordinaryHasInstance = makeCallable(
 130   Function.prototype[Symbol.hasInstance],
 131 );