I want to encrypt a string with RSA public and private keys. However, when I try to decrypt the characters back to there initial ascii-value, they return something different. Here are my methods for encrypting and decrypting:

/**
 * Method to encrypt a string using associated public-key
 * @param plainText string to cipher
 * @returns string of encrypted plainText
 */
public encryptData(plainText: string): string {
    let cipher = "";
    for (let i = 0; i < plainText.length; i++) {
        console.log(plainText.charCodeAt(i));
        let temp: number = Math.pow(plainText.charCodeAt(i), this.e) % this.n;
        console.log(String.fromCharCode(temp).charCodeAt(i));
        cipher += String.fromCharCode(temp);
    }
    return cipher;
}

/**
 * Method to decrypt a string using associated private-key
 * @param cipherText string to decrypt
 * @returns string of encrypted plainText
 */
public decryptData(cipherText: string): string {
    let text = "";
    for (let i = 0; i < cipherText.length; i++) {
        console.log(cipherText.charCodeAt(i));
        let temp: number = Math.pow(cipherText.charCodeAt(i), this.d) % this.n;
        text += String.fromCharCode(temp);
    }
    return text;
}

n, e and d are 15, 7 and 13 respectively. Any advice on this would be greatly appreciated!

EDIT

Found a solution to the problem, use the following in method when creating variable temp.

private modular_pow(base: number, expo: number, modulo: number) {
    base = base % modulo;
    var result = 1;
    var x = base;
    while(expo > 0){
        var leastSignificantBit = expo % 2;
        expo = Math.floor(expo / 2);
        if (leastSignificantBit == 1) {
            result = result * x;
            result = result % modulo;
        }
        x = x * x;
        x = x % modulo;
    }
    return result;
}