Error Checker

checkUtility.ts

const typeError = (obj: any) =>
    new Error(`check()'s first argument must be a boolean but argument was of type ${typeof obj}`);

const isNotTypeBoolean = (arg: any) => typeof arg !== 'boolean';

/**
 * Helper function for throwing errors if a given expression evaluates to false.
 * This function is strict and will throw an error the the type of the first
 * argument is not "boolean".
 */
export const check = (predicate: boolean, error: Error) => {
    if (isNotTypeBoolean(predicate)) {
        throw typeError(predicate);
    } else if (predicate) {
        return;
    }

    throw error;
};

usage.ts

export const errorMissingId: Error = new Error('A non-empty \'id\' must be provided in the request body');

check(id != null, errorMissingId);