Add js enums

blog_posts/javascript-await-timeout.md

@@ -1,7 +1,7 @@
 ---
 title: How can I add a timeout to a promise in JavaScript?
 type: question
-tags: javascript,promise,timeout
+tags: javascript,promise,timeout,class
 authors: chalarangelo
 cover: blog_images/walking.jpg
 excerpt: Oftentimes you might need to add a timeout to a promise in JavaScript. Learn how to do this and more in this short guide.

blog_posts/javascript-enum.md

@@ -0,0 +1,59 @@
+---
+title: How can I define an enum in JavaScript?
+type: question
+tags: javascript,object,class,symbol,generator
+authors: chalarangelo
+cover: blog_images/book-chair.jpg
+excerpt: Enums are part of TypeScript, but what about defininf enums in plain old JavaScript? Here are a few way you can do that.
+---
+
+TypeScript's enums are a very convenient feature present in many other languages. JavaScript, however, does not have a similar concept at this time. But what JavaScript lacks in syntactic sugar it makes up for in terms of flexibility.
+
+The easiest way to define an enum would be to use `Object.freeze()` in combination with a plain object. This will ensure that the enum object cannot be mutated.
+
+```js
+const daysEnum = Object.freeze({
+  monday: 0,
+  tuesday: 1,
+  wednesday: 2,
+  thursday: 3,
+  friday: 4,
+  saturday: 5,
+  sunday: 6
+});
+```
+
+Taking this one step further, one could extract the logic into a function with a variable number of arguments and producing a frozen object. There is very little benefit to this technique, so a better alternative would be to create a simple `class`. After all, enums are more common in object-oriented programming languages, so this sounds like a great fit.
+
+An `Enum` class would only require a `constructor` with a variable number of arguments. Its job is to add each key to the enum object and freeze the newly created instance. A potential enhancement would be to provide access to the enum values as strings. Obviously, this can be accomplished using `Object.keys()`, but a named method could result in a conflict with one of the enum's values, let alone the method polluting the result.
+
+Using an ES6 symbol is the obvious solution here, as it will not pollute the result of `Object.keys()` and it will never conflict with any values in the enum. Taking this one step further, `Symbol.iterator` would be a great choice as it would allow for the enum to be considered iterable and make it even more useful. Putting all of this together, here's my `Enum` class and how to use it:
+
+```js
+class Enum {
+  constructor(...keys) {
+    keys.forEach((key, i) => {
+      this[key] = i;
+    });
+    Object.freeze(this);
+  }
+
+  *[Symbol.iterator]() {
+    for (let key of Object.keys(this)) yield key;
+  }
+}
+
+const daysEnum = new Enum(
+  'monday',
+  'tuesday',
+  'wednesday',
+  'thursday',
+  'friday',
+  'saturday',
+  'sunday'
+);
+
+const days = [...daysEnum]; // Array of the enum values as strings
+```
+
+**Image credit:** [Taylor Simpson](https://unsplash.com/@taylorgsimpson?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText) on [Unsplash](https://unsplash.com?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText)