how memoize in js code example

Example: memoization javascript

// a simple pure function to get a value adding 10
const add = (n) => (n + 10);
console.log('Simple call', add(3));
// a simple memoize function that takes in a function
// and returns a memoized function
const memoize = (fn) => {
  let cache = {};
  return (...args) => {
    let n = args[0];  // just taking one argument here
    if (n in cache) {
      console.log('Fetching from cache');
      return cache[n];
    }
    else {
      console.log('Calculating result');
      let result = fn(n);
      cache[n] = result;
      return result;
    }
  }
}
// creating a memoized function for the 'add' pure function
const memoizedAdd = memoize(add);
console.log(memoizedAdd(3));  // calculated
console.log(memoizedAdd(3));  // cached
console.log(memoizedAdd(4));  // calculated
console.log(memoizedAdd(4));  // cached