@naturalcycles/nodejs-lib/dist/stream/transform/transformTap.js

Standard library for Node.js

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.transformTap = void 0;
const stream_1 = require("stream");
/**
 * Similar to RxJS `tap` - allows to run a function for each stream item, without affecting the result.
 * Item is passed through to the output.
 *
 * Can also act as a counter, since `index` is passed to `fn`
 */
function transformTap(fn, opt = {}) {
    const { logger = console } = opt;
    let index = -1;
    return new stream_1.Transform({
        objectMode: true,
        ...opt,
        async transform(chunk, _, cb) {
            // console.log('tap', chunk)
            try {
                await fn(chunk, ++index);
            }
            catch (err) {
                logger.error(err);
                // suppressed error
            }
            cb(null, chunk); // pass through the item
        },
    });
}
exports.transformTap = transformTap;