vault backup: 2022-10-24 18:48:10

content/notes/javascript.md

@@ -5,11 +5,53 @@ tags:
 - cosc203
 ---
 
-A scripting language to dynamically control websites.
+An dynamically typed interpreted scripting language to dynamically control websites.
 
 # HTML DOM
 (Document object model)
 - JS can access and alter HTML elements
 - When a page loads it creates the DOM as a tree of objects
 
+# Using js
+Add inline, external or internal (script tags) js
+
+loading
+- defer makes scripts run only after all scripts are loaded
+- async scripts run as soon as they are loaded (no order guaranteed)
+
+# Events
+Triggered by various things that happen on a webpage
+
+You can add an event listener to an element, which will trigger a function when that event occurs
+
+# Cookies
+Used to store data on client machines
+
+Allows server to "remember users"
+
+# Limitations
+- Cannot access client files
+- Cannot establish a connection to any server except the one it came from (apart from re-directing to a new site)
+- no multithreading
+- cannot read history
+- cannot open invisible windows
+
 # Async
+Allows running long tasks in background while browser remains responsive
+
+process
+- Call function - returns a promise immediately
+- When function is finished - we are notified and promise become a value
+
+callback: function passed to another function
+
+promise: object which represents the status of a function
+- pending
+- fulfilled -> .then
+- rejected -> .catch
+- settled (fulfilled or rejected)
+
+await: keyword within as async function which makes code wait at a point for a task to finish
+
+## Fetch
+Used to request data from a server to update the page. Data is i