objection/src/utils/decorators/memoize.js

An SQL-friendly ORM for Node.js

import upperFirst from 'lodash/upperFirst';
import {createGetter, createSetter} from '../hiddenData';

export default function memoize(target, property, descriptor) {
  const cacheProp = 'memoized' + upperFirst(property);
  const impl = descriptor.value;

  if (impl.length === 0) {
    descriptor.value = memoizeZeroArgs(impl, cacheProp);
  } else {
    descriptor.value = memoizeSingleArg(impl, cacheProp);
  }
}

function memoizeZeroArgs(impl, cacheProp) {
  const get = createGetter(cacheProp);
  const set = createSetter(cacheProp);

  return function decorator$memoize() {
    let value = get(this);

    if (value === undefined) {
      value = impl.call(this);
      set(this, value);
    }

    return value;
  };
}

function memoizeSingleArg(impl, cacheProp) {
  const get = createGetter(cacheProp);
  const set = createSetter(cacheProp);

  return function decorator$memoize(input) {
    let cache = get(this);

    if (cache === undefined) {
      cache = Object.create(null);
      set(this, cache);
    }

    if (cache[input] !== undefined) {
      return cache[input];
    } else {
      let value = impl.call(this, input);
      cache[input] = value;
      return value;
    }
  };
}