How to Specify that a Class Property is an Integer in TypeScript ?

Specifying that a class property is an integer in TypeScript involves using type annotations or specific TypeScript features to define the data type of the property.

Below are the approaches used to specify that a class property is an integer in TypeScript:

Approach 1: By using Type Annotation

Type annotation involves explicitly stating the data type of a variable or property.

Example: Here, we use the : number type annotation to specify that myIntegerProperty should be of type number. We create an instance of MyClass and log the value myIntegerProperty to the console.

class MyClass {
    myIntegerProperty: number;

    constructor(value: number) {
        this.myIntegerProperty = value;
    }
}

const myInstance = new MyClass(5);
console.log(myInstance.myIntegerProperty); 

Output:

5

Approach 2: By using Number Type Literal

Using number literal types allows you to specify a property to have a specific numeric value.

Example: Here, we use the number literal 42 to specify that myIntegerProperty should have the value 42. When creating an instance, we ensure that the property is assigned the correct value.

class MyClass {
    myIntegerProperty: 42;

    constructor() {
        this.myIntegerProperty = 42;
    }
}

const myInstance = new MyClass();
console.log(myInstance.myIntegerProperty); 

Output:

42

Approach 3: By using Enum

Enums are used to create a set of named constant values. They can be employed to restrict a property to a predefined set of integer values.

Example: We define an enum IntegerValues with specific integer values. The class property myIntegerProperty is then restricted to these enum values, ensuring it can only be assigned one of them.

enum IntegerValues {
    MyInteger = 42,
    AnotherInteger = 7,
}

class MyClass {
    myIntegerProperty: IntegerValues;

    constructor(value: IntegerValues) {
        this.myIntegerProperty = value;
    }
}

const myInstance = new MyClass(IntegerValues.MyInteger);
console.log(myInstance.myIntegerProperty); 

Output:

42

Approach 4: By using Type Alias

Type aliases allow you to create custom names for types, providing a semantic way to define integer types.

Example: Using a type alias (Integer), we create a custom type for integers. The class property myIntegerProperty is then annotated with this custom type, providing clarity and reusability.

type Integer = number;

class MyClass {
    myIntegerProperty: Integer;

    constructor(value: Integer) {
        this.myIntegerProperty = value;
    }
}

const myInstance = new MyClass(10);
console.log(myInstance.myIntegerProperty); 

Output:

10