shelving/util/transform.js

Toolkit for using data in JavaScript.

import { getDictionaryItems } from "./dictionary.js";
import { getProps } from "./object.js";
/** Modify a set of items using a transform. */
export function* mapItems(items, transform, ...args) {
    for (const item of items)
        yield transform(item, ...args);
}
/** Modify the items of an array using a transform. */
export function mapArray(arr, transform, ...args) {
    return Array.from(mapItems(arr, transform, ...args));
}
/** Modify the _values_ of the props of an object using a transform. */
export function mapProps(obj, transform, ...args) {
    return Object.fromEntries(mapEntries(getProps(obj), transform, ...args));
}
/** Modify the _values_ of a dictionary using a transform. */
export function mapDictionary(dictionary, transform, ...args) {
    return Object.fromEntries(mapEntries(getDictionaryItems(dictionary), transform, ...args));
}
/** Modify the _values_ of a set of entries using a transform. */
export function* mapEntries(entries, transform, ...args) {
    for (const e of entries)
        yield [e[0], transform(e, ...args)];
}
export function transformObject(input, transforms, ...args) {
    let changed = false;
    const output = { ...input };
    for (const [k, t] of getProps(transforms)) {
        if (t) {
            const i = input[k];
            const o = t(i, ...args);
            if (t === undefined) {
                delete output[k];
            }
            else {
                output[k] = o;
                if (!changed && i !== o)
                    changed = true;
            }
        }
    }
    return changed ? output : input;
}
/** Transform items in a sequence as they are yielded using a (potentially async) transform. */
export async function* mapSequence(sequence, transform, ...args) {
    for await (const item of sequence)
        yield transform(item, ...args);
}