Is it possible to restrict the number of entries in a JavaScript object to just two

Question

Is it possible to restrict the number of entries in a JavaScript object to just two

I have a task in my JavaScript class where I need to create a script to generate an object. The issue I am facing is that I want to restrict the possible values of a property in my object. Below is the code snippet:

var StudentObject = new Object();
var StudentStatus = new Object();
StudentStatus ={
   paid:true,
   registrationOK:true
}
StudentObject = {
   status: StudentStatus,
   track: "",
   course:"Applied Informatics"
}

In the "StudentObject" object, there is a property called "track". I want to limit its value to either "MBT" or "PBT". Is there a simple way to achieve this?

Appreciate your help.

javascript json object

Answer 1

Answer №1

It is not possible to limit the values that a public object property in javascript can hold based on how it is currently defined.

One alternative approach would be to use accessor methods for setting and retrieving the value, which could enforce constraints on what values are allowed. By storing the data within a closure that is inaccessible from outside the object, only the accessor methods would have access to it. For more information on implementing private instance variables with accessors, you can refer to .

function StudentObject(studentStatus, program) {
   // Private instance variable, only accessible internally
   var track = "";

   // Public methods
   this.setTrack = function(value) {
       if (value === "MBT" || value === "PBT") {
           track = value;
       }
   }

   this.getTrack = function() {
       return track;
   }

   this.status = studentStatus;
   this.program = program;
}

var studentStatus = {
    paid: true,
    enrollmentOK: true
}

var student = new StudentObject(studentStatus, "Applied Informatics");
student.setTrack("PBT");
alert(student.getTrack());    // "PBT"
student.setTrack("xxx");
alert(student.getTrack());    // "PBT"

Answer 2

It is not possible to limit the values that a public object property in javascript can hold based on how it is currently defined.

One alternative approach would be to use accessor methods for setting and retrieving the value, which could enforce constraints on what values are allowed. By storing the data within a closure that is inaccessible from outside the object, only the accessor methods would have access to it. For more information on implementing private instance variables with accessors, you can refer to .

function StudentObject(studentStatus, program) {
   // Private instance variable, only accessible internally
   var track = "";

   // Public methods
   this.setTrack = function(value) {
       if (value === "MBT" || value === "PBT") {
           track = value;
       }
   }

   this.getTrack = function() {
       return track;
   }

   this.status = studentStatus;
   this.program = program;
}

var studentStatus = {
    paid: true,
    enrollmentOK: true
}

var student = new StudentObject(studentStatus, "Applied Informatics");
student.setTrack("PBT");
alert(student.getTrack());    // "PBT"
student.setTrack("xxx");
alert(student.getTrack());    // "PBT"

Answer 3

Answer №2

You could potentially try this approach:

function handleTraject(x) {
    if (x === 'MBT' || x === 'PBT') {
        return x;
    } else {
        return null;
    }
}

Answer 4

You could potentially try this approach:

function handleTraject(x) {
    if (x === 'MBT' || x === 'PBT') {
        return x;
    } else {
        return null;
    }
}

Answer 5

Answer №3

This might be a bit challenging :(

You may want to reference set as well as new and Object.defineProperty

Sample Code:

function StudentInfo() {
    var _course = undefined;

    Object.defineProperties(this, {
        course: {
            enumerable: true,
            configurable: true,
            get: function () {
                return _course;
            },
            set: function (value) {
                if ((typeof(value) === "string") && (value.indexOf("Math") >= 0 || value.indexOf("Science") >= 0)) {
                    _course = value;
                }
            }
        }
    });
}

var student = new StudentInfo();
student.course = "history"; // course will not be set to history
console.log(student.course); // undefined
student.course = "mathematics"; // course will be set
console.log(student.course); // mathematics

Answer 6

This might be a bit challenging :(

You may want to reference set as well as new and Object.defineProperty

Sample Code:

function StudentInfo() {
    var _course = undefined;

    Object.defineProperties(this, {
        course: {
            enumerable: true,
            configurable: true,
            get: function () {
                return _course;
            },
            set: function (value) {
                if ((typeof(value) === "string") && (value.indexOf("Math") >= 0 || value.indexOf("Science") >= 0)) {
                    _course = value;
                }
            }
        }
    });
}

var student = new StudentInfo();
student.course = "history"; // course will not be set to history
console.log(student.course); // undefined
student.course = "mathematics"; // course will be set
console.log(student.course); // mathematics

Is it possible to restrict the number of entries in a JavaScript object to just two

Answer №1

Answer №2

Answer №3

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