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

TypeScript does not have a built-in integer type, but you can still restrict or represent integer-like values using various TypeScript features.

• All numbers in TypeScript are floating-point (number type).
• Integer-only enforcement requires custom checks or constraints.

Below are simple approaches to define numeric or controlled integer-style properties in a class.

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