Result T in TypeScript

ResultT.ts

type StringMap = Map<string, string>;

export class ResultT<T> {
    value: T | null;
    errors: StringMap;

    constructor() {
        this.value = null;
        this.errors = new Map<string, string>();
    }

    static new<T>(): ResultT<T> {
        return new ResultT();
    }

    static withValue<T>(value: T): ResultT<T> {
        const result = new ResultT<T>();
        result.value = value;
        return result;
    }

    static withErrors<T>(errors: StringMap): ResultT<T> {
        const result = new ResultT<T>();
        result.errors = errors;
        return result;
    }

    static withValueAndErrors<T>(value: T, errors: StringMap): ResultT<T> {
        const result = new ResultT<T>();
        result.value = value;
        result.errors = errors;
        return result;
    }

    static withValueAndError<T>(value: T, parameterError: string, error: string): ResultT<T> {
        const result = new ResultT<T>();
        result.value = value;
        result.errors.set(parameterError, error);
        return result;
    }

    addError(parameter: string, error: string): this {
        this.errors.set(parameter, error);
        return this;
    }

    containsErrorDescription(errorDescription: string): boolean {
        for (const error of this.errors.values()) {
            if (error === errorDescription) {
                return true;
            }
        }
        return false;
    }
}