interface IShape {
    lineCount: number
    getArea(): number
}

class Square implements IShape {
    public lineCount: number
    public sideLength: number

    constructor(sideLength: number) {
        this.sideLength = sideLength
        this.lineCount = 4;
    }

    getArea(): number {
        return this.sideLength * this.sideLength
    }
}

let square = new Square(5)
let area = square.getArea()
//area is 25

console.log(`area is ${area}`)