Use the built-in partial feature of modern setTimeout.

defer.js

@@ -16,7 +16,7 @@ function defer(func, ...args) {
   if (typeof func != 'function') {
     throw new TypeError('Expected a function');
   }
-  return setTimeout(() => func(...args), 1);
+  return setTimeout(func, 1, ...args);
 }
 
 export default defer;

delay.js

@@ -19,7 +19,7 @@ function delay(func, wait, ...args) {
   if (typeof func != 'function') {
     throw new TypeError('Expected a function');
   }
-  return setTimeout(() => func(...args), toNumber(wait) || 0);
+  return setTimeout(func, toNumber(wait) || 0, ...args);
 }
 
 export default delay;