Add defer snippet

snippets/defer.md

@@ -0,0 +1,21 @@
+### defer
+
+Defers invoking a function until the current call stack has cleared.
+
+Use `window.setTimeout()` with a timeout of 1ms to add a new event to the browser
+event queue and allow the rendering engine to complete its work. Use the spread/rest (`...`)
+operator to supply the function with an arbitrary number of arguments.
+
+```js
+const defer = (fn, ...args) => setTimeout(fn, 1, ...args);
+```
+
+```js
+// Example A:
+defer(console.log, 'a'), console.log('b'); // logs 'b' then 'a'
+
+// Example B:
+document.querySelector('#someElement').innerHTML = 'Hello';
+longRunningFunction(); // The browser will not update the HTML until this has finished
+defer(longRunningFunction); // The browser will update the HTML then run the function
+```