Caesar Cipher

caesarcipher.ts

class CaesarCipher {
    private characters = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
    private shift = 4;

    public decrypt(value: string): string {
        return value.toString().split("")
            .map(v => this.shiftNumber(Number(v))).join("");
    }

    private shiftNumber(x: number): number {
        let char = this.characters[this.characters.indexOf(x)]-this.shift;
        if (char < 0) {
            char = this.characters.slice(char)[0];
        }
        return char;
    }
}

export default CaesarCipher;