static replaceCharAt(string, index, newCharacter) {
        return `${string.substr(0, index)}${newCharacter}${string.substr(index + newCharacter.length)}`;
    }
Replace the character at the position `index` in the string `string` by the character(s) `newCharacter`.

@param {string} string
@param {int} index
@param {string} newCharacter
@returns {string}