Assignment 10 - Arrays and Records

1. Arrays

   An array contains similar elements in a large quantity. In JavaScript, they are numbered from 0 to n-1 where n is the length of the array. If the array has the name allemployees, then one can access the first element as allemployees[0], the second element as allemployees[1], and so on. The length of the array can be obtained by a method belonging to the array object as follows: n = allemployees.length - the methods referring to the object allemployees are all marked by adding a dot . and the name of the method to the variable name allemployees. In this case the method has the name length.

2. Records

   A record contains various datas belonging to the same object. Accessing these data is in JavaScript the same as accessing a method - the only difference is that one can also write values into the method which is normally not possible. The word object refers to both: the abstract data type it represents and a variable taking an instance of this data type. In this assignment, the employee data type is defined by the following constructor function employee(fn, sl, io) as:

   function employee(fn, sl, io)
   {
       this.fullname = fn;
       this.salary = sl; 
       this.isowner = io;
   }
   

   The this keyword refers to the object created by the constructor function and this.fullname to the value the full name field will have. Now, one can create an employee emp as follows:

   var emp = employee("Gerald Gugelhupf", 2233.44, false);
   

   who then has the full name Gerald Gugelhupf, earns SGD 2233.44 per month but is not considered to be an owner.

3. Array of Records

   The data structure in this assignment is an array of records. It is initialized as follows:

   allemployees = new Array(5);
   allemployees[0] = new employee("Anneliese Aal", 1324.35, false);
   allemployees[1] = new employee("Boris Bratling", 1122.44, false);
   … 
   

   So allemployees consists of 6 entries with indices 0 to 5. The data stored in the first two entries is the following:

   • allemployees[0] — Employee Name: Anneliese Aal; Salary: SGD 1324.35; Not an owner.
   • allemployees[1] — Employee Name: Boris Bratling; Salary: SGD 1122.44; Not an owner.

   The following boolean condition is true:

   allemployees[1].fullname == "Boris Bratling"
   

   So the dot symbol and the field name for the record come after the index number to identify the correct array element.

4. Getting Started.

   Please refer to this page for information on how to work on your assignment.

5. Add the age of the employees

   Each employee should have an age. So change the employee() function such that it also assigns a number to this.age. This number should be a parameter of the calling functions. Add for each employee a value for the age; it should be some number between 25 and 65. Adapt the employeeprint() function such that it also prints the age of the employee.

6. Add a new employee

   Modify the length of the array to 7. Furthermore, assign to the new employee the name Herbert Hering and the salary SGD 1100.22. His age is 35.

7. Have two owners

   Change the program such that Eberhard Ei and Claudia Creme are both owners of the company. Both owners have a salary from their own company (as already implemented).

8. Write a loop which lists the owners

   It should scan through the allemployees array and list those employees which are owners. You can read the code for the function to sum the salary for seeing how this is done.

References

Slides 48 - 58 of the Third Lecture: ps-file and pdf-file.

Pages 33-35 of Chapter 2 in Algorithmics, The Spirit of Computing.

Modules 8 and 11 in Java Script, A Beginner's Guide.