Calculator with Method Chaining — TypeScript

// Time:  O(1)
// Space: O(1)

class Calculator {
    #value : number
  
    constructor(value : number) {
        this.#value = value;
    }
    
    add(value : number) : Calculator {
        this.#value += value;
        return this;
    }
    
    subtract(value : number) : Calculator {
        this.#value -= value;
        return this;
    }
    
    multiply(value : number) : Calculator {
        this.#value *= value;
        return this;
    }

    divide(value : number) : Calculator {
        if (value === 0) {
            throw new Error("Division by zero is not allowed");
        }
        this.#value /= value;
        return this;
    }
    
    power(value : number) : Calculator {
        this.#value **= value;
        return this;
    }

    getResult() : number {
        return this.#value;
    }
}