Added new post "Iterating over Object properties in JavaScript"

Author: nikhilmopidevi

_posts/2020-04-13-Iterating over Object properties in JavaScript.markdown

@@ -0,0 +1,99 @@
+---
+layout: post
+title: "Iterating over Object properties in JavaScript"
+date: 2020-04-13 20:00:00 -0700
+tags: [JavaScript, Object]
+comments: true
+---
+
+There are several ways to iterate over an object's properties in JavaScript.
+
+[Object.entries()][Object.entries()] returns an array of object's own enumerable string-keyed property `[key, value]` pairs. This array can then be iterated over using [forEach()][Array.prototype.forEach()] or [for...of][for...of].
+
+## Example
+
+{% highlight javascript %}
+
+const book = {
+  "title": "The Fountainhead",
+  "author": "Ayn Rand",
+  "pages": 753
+};
+
+Object.entries(book).forEach(([key, value]) => {
+  console.log(`${key}: ${value}`);
+});
+
+{% endhighlight %}
+
+## Output
+
+{% highlight javascript %}
+
+title: The Fountainhead
+author: Ayn Rand
+pages: 753
+
+{% endhighlight %}
+
+Similarly, `for...of` can also be used with `Object.entries()`.
+
+{% highlight javascript %}
+
+for (let [key, value] of Object.entries(book)) {
+  console.log(`${key}: ${value}`);
+}
+
+{% endhighlight %}
+
+## for...in
+
+`for...in` statement can also be used to iterate over object properties, but it also iterates over inherited properties. Luckily, [hasOwnProperty()][hasOwnProperty()] method can be used to check if a property is object's own property.
+
+{% highlight javascript %}
+
+const book = {
+  "title": "The Fountainhead",
+  "author": "Ayn Rand",
+  "pages": 753
+};
+
+for (let key in book) {
+  if (book.hasOwnProperty(key)) {
+    console.log(`${key}: ${book[key]}`);
+  }
+}
+
+{% endhighlight %}
+
+## Object.keys() and Object.values()
+
+If we are only concerned with object property keys, then `Object.keys()` can be used. Similarly, `Object.values()` can be used to get object property values.
+
+{% highlight javascript %}
+
+const book = {
+  "title": "The Fountainhead",
+  "author": "Ayn Rand",
+  "pages": 753
+};
+
+Object.keys(book).forEach(key => {
+  console.log(key);
+});
+
+Object.values(book).forEach(value => {
+  console.log(value);
+});
+
+{% endhighlight %}
+
+
+[Object.entries()]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries
+{:target="_blank"}
+[Array.prototype.forEach()]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach 
+{:target="_blank"}
+[for...of]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of 
+{:target="_blank"}
+[hasOwnProperty()]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty
+{:target="_blank"}