option-t/esm/nullable/operators/map_or.js

A toolkit of Nullable/Option/Result type implementation in ECMAScript. Their APIs are inspired by Rust's `Option<T>` and `Result<T, E>`.

import { expectNotNull } from '../core/nullable.js';
import { ERR_MSG_TRANSFORMER_MUST_NOT_RETURN_NO_VAL_FOR_NULLABLE, ERR_MSG_DEFAULT_VALUE_MUST_NOT_BE_NO_VAL_FOR_NULLABLE, } from '../internal/error_message.js';
/**
 *  Return the result of _transformer_ with using _input_ as an argument for it if _input_ is not `null`.
 *  Otherwise, return _defaultValue_.
 *
 *  Basically, this operation is a combination `map()` and `unwrapOr()`.
 *
 *  * `U` must not be `Nullable<*>`.
 *      * If the result of _transformer_ is `null`, this throw an `Error`.
 *      * If the result of _defaultValue_ is `null`, this throw an `Error`.
 *  * If you'd like to accept `Nullable<*>` as `U`, use a combination `andThen()` and `or()`.
 */
export function mapOrForNullable(input, defaultValue, transformer) {
    let result;
    let msg = '';
    if (input !== null) {
        result = transformer(input);
        msg = ERR_MSG_TRANSFORMER_MUST_NOT_RETURN_NO_VAL_FOR_NULLABLE;
    }
    else {
        result = defaultValue;
        msg = ERR_MSG_DEFAULT_VALUE_MUST_NOT_BE_NO_VAL_FOR_NULLABLE;
    }
    const passed = expectNotNull(result, msg);
    return passed;
}