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import groupByLimit from './groupByLimit';
/**
* Returns a new object, where each value corresponds to an array of items, from
* `coll`, that returned the corresponding key. That is, the keys of the object
* correspond to the values passed to the `iteratee` callback.
*
* Note: Since this function applies the `iteratee` to each item in parallel,
* there is no guarantee that the `iteratee` functions will complete in order.
* However, the values for each key in the `result` will be in the same order as
* the original `coll`. For Objects, the values will roughly be in the order of
* the original Objects' keys (but this can vary across JavaScript engines).
*
* @name groupBy
* @static
* @memberOf module:Collections
* @method
* @category Collection
* @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
* @param {AsyncFunction} iteratee - An async function to apply to each item in
* `coll`.
* The iteratee should complete with a `key` to group the value under.
* Invoked with (value, callback).
* @param {Function} [callback] - A callback which is called when all `iteratee`
* functions have finished, or an error occurs. Result is an `Object` whoses
* properties are arrays of values which returned the corresponding key.
* @returns {Promise} 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
*
* const files = ['dir1/file1.txt','dir2','dir4']
*
* // asynchronous function that detects file type as none, file, or directory
* function detectFile(file, callback) {
* fs.stat(file, function(err, stat) {
* if (err) {
* return callback(null, 'none');
* }
* callback(null, stat.isDirectory() ? 'directory' : 'file');
* });
* }
*
* //Using callbacks
* async.groupBy(files, detectFile, function(err, result) {
* if(err) {
* console.log(err);
* } else {
* console.log(result);
* // {
* // file: [ 'dir1/file1.txt' ],
* // none: [ 'dir4' ],
* // directory: [ 'dir2']
* // }
* // result is object containing the files grouped by type
* }
* });
*
* // Using Promises
* async.groupBy(files, detectFile)
* .then( result => {
* console.log(result);
* // {
* // file: [ 'dir1/file1.txt' ],
* // none: [ 'dir4' ],
* // directory: [ 'dir2']
* // }
* // result is object containing the files grouped by type
* }).catch( err => {
* console.log(err);
* });
*
* // Using async/await
* async () => {
* try {
* let result = await async.groupBy(files, detectFile);
* console.log(result);
* // {
* // file: [ 'dir1/file1.txt' ],
* // none: [ 'dir4' ],
* // directory: [ 'dir2']
* // }
* // result is object containing the files grouped by type
* }
* catch (err) {
* console.log(err);
* }
* }
*
*/
export default function groupBy (coll, iteratee, callback) {
return groupByLimit(coll, Infinity, iteratee, callback)
}
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