Update arrow_function.md

docs/JavaScript_Advance/arrow_function.md

@@ -1 +1,23 @@
-# Arrow Function
+# Arrow Function  
+An arrow function expression is a syntactically compact alternative to a regular function expression.
+
+Example:
+```javascript
+// Regular function 
+function greet(name){
+  console.log("Hello " + name);
+}
+
+// Arrow function equivalent
+const greet = name => {
+  console.log("Hello " + name)
+}
+```
+Both functions above are equivalent to each other.    
+
+If we have more than one function argument then we should put them in paranthesis like this:
+```javascript
+const exampleFunc = (name,age,eyeColor) => {
+  // ...
+}
+```