add built in functions

geekysrm · geekysrm · commit 687e8a457c58 · 2019-12-25T22:46:04.000+05:30
diff --git a/11-functions-built-in.md b/11-functions-built-in.md
@@ -0,0 +1,61 @@
+## Functions - Built in
+
+-   Function allows us to _group together multiple statements,_ take in some values, perform some operations and return some value.
+    
+-   Functions take in data known as _arguments._
+    
+-   Function may or may not _return_ a value.
+    
+-   Example:
+    
+    ```javascript
+      Math.max(10, 12); // 12
+    
+    ```
+    
+    The above line is a JavaScript statement.
+    
+    10 and 12 passed to the function are arguments, separated by comma.
+    
+    12 is _returned_ from the function.
+    
+-   There are many in-built JavaScript functions.
+    
+    e.g:
+    
+    -   `console.log('hey');` returns `undefined` , logs `hey`.
+    -   `parseFloat('2.032565') // 2.032565` (converts string to number)
+    -   `parseInt('2.032565') // 2` (converts string to number as integer)
+    -   Many date functions are also present. e.g. `Date.now()` returns no. of milliseconds since January 1, 1970 00:00:00 UTC.
+    -   DOM functions:
+        -   Example:
+            
+            ```html
+              <body>
+              <p>Hey How ya doin?</p>
+              	<script>
+              		const para = document.querySelector('p'); // finds p tag in page
+              		console.log(para); // <p>Hey How ya doin?</p>
+              	</script>
+              </body>
+            
+            ```
+            
+        -   Mobile only functions e.g. `navigator.vibrate()`
+            
+-   In case of doubts, always refer MDN Docs.
+    
+-   Other Examples:
+    
+    ```javascript
+      scrollTo(0, 200); // scrolls to (x, y) position in page
+      
+      scrollTo({
+      	top: 500,
+      	left: 0,
+      	behavior: 'smooth'
+      }); // scrolls to position top: 500, left: 0 in a 'smooth' manner
+    
+    ```
+    
+    The `scrollTo` function returns `undefined`.
