Add once snippet

snippets/once.md

@@ -0,0 +1,27 @@
+### once
+
+Ensures a function is called only once.
+
+Utilizing a closure, use a variable flag and set it to true once the function is called
+for the first time, preventing it from being called again. Allow the function to be supplied
+with an arbitrary number of arguments using the spread/rest (`...`) operator.
+
+```js
+const once = fn => {
+  let called = false;
+  return (...args) => {
+    if (!called) {
+      fn(...args);
+      called = true;
+    }
+  };
+};
+```
+
+```js
+const startApp = event => {
+  // initializes the app
+  console.log(event); // access to any arguments supplied
+};
+document.addEventListener('click', once(startApp)); // only runs `startApp` once upon click
+```

tag_database

@@ -95,6 +95,7 @@ negate:logic
 nthElement:array
 objectFromPairs:object
 objectToPairs:object
+once:function
 onUserInputChange:browser
 orderBy:object
 palindrome:string