Overview

Implement memoize(fn) that returns a function caching results based on the first argument.

Constraints

• Cache key is first argument (use it directly)
• Return cached result if same key is called again

Examples

const double = memoize(x => x * 2);
double(5); // 10 (computed)
double(5); // 10 (cached)

Solution

function memoize(fn) {
  const cache = new Map();
  return function(arg) {
    if (cache.has(arg)) return cache.get(arg);
    const result = fn(arg);
    cache.set(arg, result);
    return result;
  };
}