<pre class="shiki github-dark shaku"><code>/** * @param {Function} func * @param {(args:[]) =&gt; string } [resolver] - cache key generator */function memo(func, resolver) { let funcMap = new Map(); return function(...args) { // use rest operator as it converts parameter to array and join can be applied only on arrays let mapKey = resolver ? resolver(...args) : args.join('_') let isCached = funcMap.has(mapKey) if(isCached) { return funcMap.get(mapKey) } // let res = func.call(this,...args) //use spread operator since its call let res = func.apply(this,args) funcMap.set(mapKey, res) return res }}</code></pre>