Javascript keeps outputting wrong array index
I am trying to finish an assignment, I am stuck and cannot find a solution. Below is my complete code.
//Student Object
var student = {
f_name: "",
l_name: "",
s_numb: "",
email: "",
courses: [],
/*This function returns if current object has a specific course
and returns true if it does and false if not.*/
hasCourse: function (course) {
for (var c = 0; c < this.courses.length; c++) {
if (course == this.courses[c]) {
return true;
}
}
return false;
}
};
/*This function returns name with first letter
capitalized and the rest lowercase.*/
function formatingName(name) {
return name.charAt(0).toUpperCase() + name.substr(1, name.length);
}
/*This function validates to match the Student ID pattern and
returns true it matches and false if not.*/
function validateStudentID(sid) {
var patt = /^([0-9]{3}[.]){2}[0-9]{3}$/;
return patt.test(sid);
}
/*This function receives a string array of course codes which
are to be registered for a student. The function returns an empty
string indicating all course codes in the array are valid; otherwise
the function returns the first invalid course code in the array.*/
function validateCourses(courses) {
var error = false;
for (i = 0; i < courses.length; i++) {
if (error == false) {
if (courses[i] != "APC100" && courses[i] != "IPC144" &&
courses[i] != "ULI101" && courses[i] != "IOS110" &&
courses[i] != "EAC150" && courses[i] != "IBC233" &&
courses[i] != "OOP244" && courses[i] != "DBS201" &&
courses[i] != "INT222") {
error = courses[i];
break;
}
}
}
if (error != false) {return error;} else {return "";}
return '';
}
var response = true; //Continues to prompt if error is true
var error = false; //Error flag
var temp_obj = []; //Temporary object that hold current object values
var temp_course = [];
var students = [];
var x = 0;
while (response == true) {
do {
var str = prompt("Please enter first name, last name, student ID,\nemail and courses (separated by ',')");
if (str == "" || str === null) {
response = false;
break;
}
//Removing white spaces in the string
str = str.split(' ').join('');
//Splitting the string into array by , (coma) and assigning it to temporary object array
temp_obj = str.split(',');
//Validating Student ID
if (validateStudentID(temp_obj[2]) == false) {
alert(temp_obj[2] + " is not a valid student ID, Please use xxx.xxx.xxx format.\nPlease try again!");
error = true;
}
//Validating if student is registered in atleast 1 course.
if (temp_obj.length < 5) {
alert("A student must be registered in at-least 1 course");
error = true;
}
//Checking if student is registered in more than 6 courses
if (temp_obj.length > 10) {
temp_obj = temp_obj.slice(0,9);
}
//Extracting courses from temporary object array
temp_course = temp_obj.slice(4, temp_obj.length);
//Makking all the courses uppercase
for (i = 0; i < temp_course.length; i++) {
temp_course[i] = temp_course[i].toUpperCase();
}
//Validating if courses are valid
if (validateCourses(temp_course) != "") {
alert(validateCourses(temp_course) + " is not the course provided by CPD program!\nPlease try again.");
error = true;
}
}
while (error == true);
//Break out of loop if user submitted nothing or if user pressed cancel
if (response == false) {break;}
//Merging cources array back with temporary object array
temp_obj = temp_obj.concat(temp_course);
//Creating a new instance of a student
students[x] = Object.create(student);
//Assigning values to student object from temporary object;
students[x].f_name = formatingName(temp_obj[0]); //Formatting name
students[x].l_name = formatingName(temp_obj[1]);
students[x].s_numb = temp_obj[2];
students[x].email = temp_obj[3].toLowerCase(); //Making the email all lowercase
//Making the course codes in Uppercase
for (i = 0; i < (temp_obj.length) - 4; i++ ) {
students[x].courses[i] = temp_obj[i + 4].toUpperCase();
}
x++;
}
//Printing total registered students
alert("There are total " + students.length + " students registered.");
var R_fname = [];
var R_lname = [];
var R_sid = [];
var R_email = [];
do {
var no_error = false;
var query = true;
var query_course = [];
while (no_error == false) {
query = prompt("Please enter a course code:");
if (query == "" || query == null) {
query = false;
break;
}
no_error = true;
query_course[0] = query.toUpperCase();
if (validateCourses(query_course) != "") {
alert(query + " is not the course provided by CPD program!\nPlease try again");
no_error = false;
}
}
if (query == false) {break;}
//THIS IS WHERE I THINK THE PROBLEM IS
//THIS IS WHERE I THINK THE PROBLEM IS
//THIS IS WHERE I THINK THE PROBLEM IS
//THIS IS WHERE I THINK THE PROBLEM IS
for (var a = 0; a < students.length; a++) {
//Checking if student is registred in a course
if (students[a].hasCourse(query_course) == true) {
//Assigning values to temporary array.
R_fname[a] = students[a].f_name;
R_lname[a] = students[a].l_name;
R_sid[a] = students[a].s_numb;
R_email[a] = students[a].email;
}
}
var fin_str = "";
//Concatenating all the students in a specific course to fin_str as string.
for (var b = 0; b < R_fname.length; b++) {
fin_str += (R_fname[b] + " " + R_lname[b] + " " + R_sid[b] + " " + R_email[b] + " \n");
}
//Printing list of student in a specific course
alert("List of students registered in " + query + "\n\n" + fin_str);
//Retting temporary arrays
R_fname.length = 0;
R_lname.length = 0;
R_sid.length = 0;
R_email.length = 0;
//Confirms to Exit the query loop
if (confirm("Click 'OK' to continue to query class lists.\nClick 'Cancel' to stop the program.") == false) {break;}
}
while (query != false);
These are the test values:
Rua, bean, 056.171.486, rbean @ example.ca, int222
redneck, bell, 121.126.536, cbell @ example.ca, dbs201, int222
Eric, brand, 046.123.976, ebrand @ example.ca, oop244, dbs201, int222
Henry, clay, 034.146.412, hclay@example.ca , ibc233, oop244, dbs201, int222
When the program asks for a course code; it is assumed that students have this course, and only if they do, it prints information about the students.
In my case, even if the student does not have a course, he still prints it. Please run the code to see if it makes sense ... I can't explain better
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1 answer
The problem can be summarized as follows:
var Foo = {
courses: []
};
var x = Object.create(Foo);
var y = Object.create(Foo);
x.courses.push(123);
alert(y.courses[0]); // "123"
The reason for this behavior is that both objects inherit the same prototype, and any changes made to .courses
will apply to both objects.
For this reason, it would be better to create a constructor function:
function Foo()
{
this.courses = [];
}
var x = new Foo();
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