option-t/esm/deprecated/plain_option/filter.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 { isNone, createNone } from './option.js';
/**
 *  Returns `None` if the option is `None`,
 *  otherwise the result should be resolved by the result of _predicate_ with the wrapped value as the arguments:
 *
 *      * `Some(t)` if _predicate_ returns `true`.
 *      * `None` if _predicate_ returns `false`.
 */
export function filterForOption(input, predicate) {
    if (isNone(input)) {
        return input;
    }
    const ok = predicate(input.val);
    if (!ok) {
        return createNone();
    }
    const result = input;
    return result;
}