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import concatLimit from './concatLimit';
import awaitify from './internal/awaitify'
/**
* Applies `iteratee` to each item in `coll`, concatenating the results. Returns
* the concatenated list. The `iteratee`s are called in parallel, and the
* results are concatenated as they return. The results array will be returned in
* the original order of `coll` passed to the `iteratee` function.
*
* @name concat
* @static
* @memberOf module:Collections
* @method
* @category Collection
* @alias flatMap
* @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
* @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).
* @returns A Promise, if no callback is passed
* @example
*
* // dir1 is a directory that contains file1.txt, file2.txt
* // dir2 is a directory that contains file3.txt, file4.txt
* // dir3 is a directory that contains file5.txt
* // dir4 does not exist
*
* let directoryList = ['dir1','dir2','dir3'];
* let withMissingDirectoryList = ['dir1','dir2','dir3', 'dir4'];
*
* // Using callbacks
* async.concat(directoryList, fs.readdir, function(err, results) {
* if (err) {
* console.log(err);
* } else {
* console.log(results);
* // [ 'file1.txt', 'file2.txt', 'file3.txt', 'file4.txt', file5.txt ]
* }
* });
*
* // Error Handling
* async.concat(withMissingDirectoryList, fs.readdir, function(err, results) {
* if (err) {
* console.log(err);
* // [ Error: ENOENT: no such file or directory ]
* // since dir4 does not exist
* } else {
* console.log(results);
* }
* });
*
* // Using Promises
* async.concat(directoryList, fs.readdir)
* .then(results => {
* console.log(results);
* // [ 'file1.txt', 'file2.txt', 'file3.txt', 'file4.txt', file5.txt ]
* }).catch(err => {
* console.log(err);
* });
*
* // Error Handling
* async.concat(withMissingDirectoryList, fs.readdir)
* .then(results => {
* console.log(results);
* }).catch(err => {
* console.log(err);
* // [ Error: ENOENT: no such file or directory ]
* // since dir4 does not exist
* });
*
* // Using async/await
* async () => {
* try {
* let results = await async.concat(directoryList, fs.readdir);
* console.log(results);
* // [ 'file1.txt', 'file2.txt', 'file3.txt', 'file4.txt', file5.txt ]
* } catch (err) {
* console.log(err);
* }
* }
*
* // Error Handling
* async () => {
* try {
* let results = await async.concat(withMissingDirectoryList, fs.readdir);
* console.log(results);
* } catch (err) {
* console.log(err);
* // [ Error: ENOENT: no such file or directory ]
* // since dir4 does not exist
* }
* }
*
*/
function concat(coll, iteratee, callback) {
return concatLimit(coll, Infinity, iteratee, callback)
}
export default awaitify(concat, 3);
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