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import noop from './internal/noop';
import wrapAsync from './internal/wrapAsync';
import mapLimit from './mapLimit';
/**
* The same as [`concat`]{@link module:Collections.concat} but runs a maximum of `limit` async operations at a time.
*
* @name concatLimit
* @static
* @memberOf module:Collections
* @method
* @see [async.concat]{@link module:Collections.concat}
* @category Collection
* @param {Array|Iterable|Object} coll - A collection to iterate over.
* @param {number} limit - The maximum number of async operations at a time.
* @param {AsyncFunction} iteratee - A function to apply to each item in `coll`,
* which should use an array as its result. Invoked with (item, callback).
* @param {Function} [callback] - A callback which is called after all the
* `iteratee` functions have finished, or an error occurs. Results is an array
* containing the concatenated results of the `iteratee` function. Invoked with
* (err, results).
*/
export default function(coll, limit, iteratee, callback) {
callback = callback || noop;
var _iteratee = wrapAsync(iteratee);
mapLimit(coll, limit, (val, callback) => {
_iteratee(val, (err, ...args) => {
if (err) return callback(err);
return callback(null, args);
});
}, (err, mapResults) => {
var result = [];
for (var i = 0; i < mapResults.length; i++) {
if (mapResults[i]) {
result = result.concat(...mapResults[i]);
}
}
return callback(err, result);
});
}
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