Chapter 5, Prototype

Lets try and solve the following exercise:

Exercises

  1. Create an object called shape that has a type property and a getType() method:
            var shape = { 
          type: 'shape', 
          getType: function () { 
            return this.type; 
          } 
        };
  2. The following is the program for a Triangle () constructor:
            function Triangle(a, b, c) { 
          this.a = a; 
          this.b = b; 
          this.c = c; 
        } 
 
        Triangle.prototype = shape; 
        Triangle.prototype.constructor = Triangle; 
        Triangle.prototype.type = 'triangle';
  3. To add the getPerimeter() method, use the following code:
            Triangle.prototype.getPerimeter = function () { 
          return this.a + this.b + this.c; 
        };
  4. Test the following code:
            > var t = new Triangle(1, 2, 3); 
        > t.constructor === Triangle; 
        true 
        > shape.isPrototypeOf(t); 
        true 
        > t.getPerimeter(); 
        6 
        > t.getType(); 
        "triangle"
  5. Loop over t showing only own properties and methods:
            for (var i in t) { 
          if (t.hasOwnProperty(i)) { 
            console.log(i, '=', t[i]); 
         } 
        }
  6. Randomize array elements using the following code snippet:
            Array.prototype.shuffle = function () { 
          return this.sort(function () { 
            return Math.random() - 0.5; 
          }); 
        };

    Testing:

            > [1, 2, 3, 4, 5, 6, 7, 8, 9].shuffle(); 
         [4, 2, 3, 1, 5, 6, 8, 9, 7] 
        > [1, 2, 3, 4, 5, 6, 7, 8, 9].shuffle(); 
         [2, 7, 1, 3, 4, 5, 8, 9, 6] 
        > [1, 2, 3, 4, 5, 6, 7, 8, 9].shuffle(); 
         [4, 2, 1, 3, 5, 6, 8, 9, 7]
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