lib/internal/util/types.js


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'use strict';

const ReflectApply = Reflect.apply;

// This function is borrowed from the function with the same name on V8 Extras'
// `utils` object. V8 implements Reflect.apply very efficiently in conjunction
// with the spread syntax, such that no additional special case is needed for
// function calls w/o arguments.
// Refs: https://github.com/v8/v8/blob/d6ead37d265d7215cf9c5f768f279e21bd170212/src/js/prologue.js#L152-L156
function uncurryThis(func) {
  return (thisArg, ...args) => ReflectApply(func, thisArg, args);
}

const TypedArrayPrototype = Object.getPrototypeOf(Uint8Array.prototype);

const TypedArrayProto_toStringTag =
    uncurryThis(
      Object.getOwnPropertyDescriptor(TypedArrayPrototype,
                                      Symbol.toStringTag).get);

// Cached to make sure no userland code can tamper with it.
const isArrayBufferView = ArrayBuffer.isView;

function isTypedArray(value) {
  return TypedArrayProto_toStringTag(value) !== undefined;
}

function isUint8Array(value) {
  return TypedArrayProto_toStringTag(value) === 'Uint8Array';
}

module.exports = {
  isArrayBufferView,
  isTypedArray,
  isUint8Array
};