it-reduce/dist/src/index.js

Reduces the values yielded from an async iterator

/**
 * @packageDocumentation
 *
 * Reduce the values of an (async)iterable to a single value.
 *
 * @example
 *
 * ```javascript
 * import reduce from 'it-reduce'
 *
 * // This can also be an iterator, generator, etc
 * const values = [0, 1, 2, 3, 4]
 *
 * const result = reduce(values, (acc, curr, index) => acc + curr, 0)
 *
 * console.info(result) // 10
 * ```
 *
 * Async sources must be awaited:
 *
 * ```javascript
 * import reduce from 'it-reduce'
 *
 * const values = async function * () {
 *   yield * [0, 1, 2, 3, 4]
 * }
 *
 * const result = await reduce(values(), (acc, curr, index) => acc + curr, 0)
 *
 * console.info(result) // 10
 * ```
 */
function isAsyncIterable(thing) {
    return thing[Symbol.asyncIterator] != null;
}
function reduce(source, func, init) {
    let index = 0;
    if (isAsyncIterable(source)) {
        return (async function () {
            for await (const val of source) {
                init = func(init, val, index++);
            }
            return init;
        })();
    }
    for (const val of source) {
        init = func(init, val, index++);
    }
    return init;
}
export default reduce;
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