Memoize very similar to `useMemo` in React

memo.js

function isEqual(prevDeps = [], newDeps = []) {
  if (prevDeps.length !== newDeps.length) {
    return false;
  }

  for (const [ i, dep ] of newDeps.entries()) {
    if (!Object.is(dep, prevDeps[i])) {
      return false;
    }
  }

  return true;
}

const createMemo = () => {
  let memoizedState = null;
  
  function memo(createFn, deps = []) {
    const prevState = memoizedState;
    let nextState;
    
    if (prevState && isEqual(deps, prevState.deps)) {
      console.log('Using memoised result');
      return prevState.result;
    } else {
      console.log('Calculating again');
      nextState = {
        result: createFn(),
        deps
      };

      memoizedState = nextState;
      return memoizedState.result;
    }
  }

  return memo;
};


// Example 
const memo = createMemo();

let a = 40, b = 50; 
let result = memo(() => a + b, [a, b]);
// Calculating: 90

let result = memo(() => a + b, [a, b]);
// Using memoized value: 90

a = 50;

let result = memo(() => a + b, [a, b]);
// Calculating: 100