@skele/classic/src/impl/memoize-one.js

Skele is an architectural framework that assists with building data-driven apps with React or React Native.

// MIT License

// Copyright (c) 2017 Alexander Reardon

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

const simpleIsEqual = (a, b) => a === b

// <ResultFn: (...Array<any>) => mixed>
// The purpose of this typing is to ensure that the returned memoized
// function has the same type as the provided function (`resultFn`).
// ResultFn:        Generic type (which is the same as the resultFn).
// (...Array<any>): Accepts any length of arguments - and they are not checked
// mixed:           The result can be anything but needs to be checked before usage
export default function memoizeOne(resultFn, isEqual = simpleIsEqual) {
  let lastThis
  let lastArgs = []
  let lastResult
  let calledOnce = false

  const isNewArgEqualToLast = (newArg, index) =>
    isEqual(newArg, lastArgs[index])

  // breaking cache when context (this) or arguments change
  const result = function(...newArgs) {
    if (
      calledOnce &&
      lastThis === this &&
      newArgs.length === lastArgs.length &&
      newArgs.every(isNewArgEqualToLast)
    ) {
      return lastResult
    }

    // Throwing during an assignment aborts the assignment: https://codepen.io/alexreardon/pen/RYKoaz
    // Doing the lastResult assignment first so that if it throws
    // nothing will be overwritten
    lastResult = resultFn.apply(this, newArgs)
    calledOnce = true
    lastThis = this
    lastArgs = newArgs
    return lastResult
  }

  return result
}