Webprog

• Objects


  Used for named properties that give multiple values
• Creating an empty object

  var myCar{}; or var myCar = new Object();
• Using dot syntax


  myCar.make = "Toyota";
• Using bracket notation


  let myCar = {}; myCar.make = "Ford"; myCar["make"] = "Ford";
• Creating complex objects


  let props = ["make", "model"]; let vals = ["Audi", "A6"]; for (let i=0; i<props.length; i++){anotherCar[props[i]] = vals[i];}
• Objects vs Arrays


  Both hold multiple pieces of data. Arrays hold a collection of things. Arrays with indexes dont benefit of being descriptive.
• Complex objects


  Can be made up of scalar properties such as strings, integers and booleans. Arrays can be made up of objects, other arrays and scalar values.
• JSON vs JavaScript Objects

  JSON: Properties/keys must be string written double quotes. JSON: Can have string, numbers, JSON object, array, null and boolean. JavaScript Objects: Not written with double quotes. JavaScript Objects: Can contains javascript values/types such as functions.
• Using square bracket notation

  let student = { id: 119, firstName: "Nik", surname: "C-K" }; console.log(student["surname"] + ", " + student["firstName"]);
• Traversing object properties


  for (let key in sydney){ console.log(key + "=" + sydney[key]); } if ("termNumber" in sydney){ console.log(sydney.termNumber); } else console.log("no term number");
• Accessors/Mutators


  Use get and set as keywords. get total(){ return this.price * this.quantity; }
• this keyword


  Access an object's members from inside an object definition
• class keyword


  Uses prototypal inheritance
• Using accessors/mutators


  get/set. Warning about setters: use different names for assigning variables and property names. get area(){ return Math.PI * this.radius ** 2; }
• Object.keys()


  Accepts object and returns array of keys
• Object.values()


  Accepts an object and returns array of values
• Object.entries()


  Accepts an object, returns an array where each element is an array with 2 elements (key, value)
• Bash is installed when installing git
• node -v checks if node is installed
• npm -v checks if node package manager is installed
• npm init


  Initializes package manager
• node app.js


  Used to run command line applications
• Installing packages


  Downloading pre-existing files
• Purpose of packages


  Node.js allows to add additional libraries to app without code functionality
• Using "express" library


  Simplifies starting a server and managing requests/responses
• npm install express


  Downloads node_modules, makes an entry in the package.json file, creates node_modules if it doesn't exist, package.json has a record now, package runs dependency/library
• Starting server apps


  const express = require('express') const app = express() app.listen(3000, () => { console.log('listening on port 3000') })
• Routing requests


  Associates an incoming url with a function. Views folder is made for hbs/html like files.
• Express routes


  app.get("/your-route", (req, res) => {}); app.post("/your-request", (req,res) => {});
• Express responses


  res.send("text or HTML"); res.render("template-file", {variable:value1, variable2:value2});
• Serving static files


  app.use(express.static("public"));
• Getting information from URL

  req.params contains route parameters in the url. req.query contains query parameters in url query string. req.body retrieves client's request from app.post();
• GET method


  Data sent through url using query. Limited amount can be sent. Everything is visible in the url, not good for confidential info. Used for retrieving data that don't change server's state. Good for sharing/bookmarking data visible in the url.
• POST method


  Data is sent in the body of HTTP request. No limited amount of data that can be sent. Data is not visible in the url, good for confidential info. Submit forms/operations that changes server's state. Not good for sharing/bookmarking data since invisible in url.
• Testing routes is done by typing in the url or submitting forms
• MySQL databases


  Use tables to organize data
• Primary Key


  Uniquely identifies a record in a table
• INT(M)


  Integer data type, M is the max value
• CHAR(M)


  Fixed string length, M represents the exact column length in chars
• VARCHAR(M)


  Variable length string, M represents the maximum column length in characters