Classes

• This is part of chapter 6 of the book.
• Classes are evolving in javascript.

• class Name {
      member = value; // but only constant assigns.
      member = value;
      constructor(params) {
      }
  
      name(params){
      }
      ...
  } 

  • Note, no "function" in member function definitions.
  • Constructor is named constructor
  • Also annoying, member data.

    • this.data = datavalue.
                    

    • Allways reference with the this. format
  • If there is a member variable foo

    • get foo()  {
        ... 
      } 

    • Defines a getter for foo.

    • set foo()  {
        ... 
      } 

    • Note, these can not be the same as the propery name. (drats)
    • But you can call them with =
  • Take a look at the point class in nine.js

  • let canvas = document.getElementById("polygons");
    let ctx = canvas.getContext('2d');
    let cx = canvas.width/2;
    let cy = canvas.height/2;
    
    let shapes = [];
    let r = 10;
    
    // build the shapes
    for(let sides =3; sides < 20; sides ++) {
        shapes.push(new Shape(sides, r));
        r += 10;
    }
    
    // apply a random color to the shapes
    for(let i=0; i < shapes.length; i++) {
        shapes[i].RandomColor();
    }
    
    // display the shapes.
    for (let i=0; i < shapes.length; i++) {
        shapes[i].Display(ctx, cx, cy);
    }
              

  • Look at the Shape class in nine.js