Async.js

each.js

  1. import eachOf from './eachOf.js'
  2. import withoutIndex from './internal/withoutIndex.js'
  3. import wrapAsync from './internal/wrapAsync.js'
  4. import awaitify from './internal/awaitify.js'
  6. /**
  7.  * Applies the function `iteratee` to each item in `coll`, in parallel.
  8.  * The `iteratee` is called with an item from the list, and a callback for when
  9.  * it has finished. If the `iteratee` passes an error to its `callback`, the
  10.  * main `callback` (for the `each` function) is immediately called with the
  11.  * error.
  12.  *
  13.  * Note, that since this function applies `iteratee` to each item in parallel,
  14.  * there is no guarantee that the iteratee functions will complete in order.
  15.  *
  16.  * @name each
  17.  * @static
  18.  * @memberOf module:Collections
  19.  * @method
  20.  * @alias forEach
  21.  * @category Collection
  22.  * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
  23.  * @param {AsyncFunction} iteratee - An async function to apply to
  24.  * each item in `coll`. Invoked with (item, callback).
  25.  * The array index is not passed to the iteratee.
  26.  * If you need the index, use `eachOf`.
  27.  * @param {Function} [callback] - A callback which is called when all
  28.  * `iteratee` functions have finished, or an error occurs. Invoked with (err).
  29.  * @returns {Promise} a promise, if a callback is omitted
  30.  * @example
  31.  *
  32.  * // dir1 is a directory that contains file1.txt, file2.txt
  33.  * // dir2 is a directory that contains file3.txt, file4.txt
  34.  * // dir3 is a directory that contains file5.txt
  35.  * // dir4 does not exist
  36.  *
  37.  * const fileList = [ 'dir1/file2.txt', 'dir2/file3.txt', 'dir/file5.txt'];
  38.  * const withMissingFileList = ['dir1/file1.txt', 'dir4/file2.txt'];
  39.  *
  40.  * // asynchronous function that deletes a file
  41.  * const deleteFile = function(file, callback) {
  42.  *     fs.unlink(file, callback);
  43.  * };
  44.  *
  45.  * // Using callbacks
  46.  * async.each(fileList, deleteFile, function(err) {
  47.  *     if( err ) {
  48.  *         console.log(err);
  49.  *     } else {
  50.  *         console.log('All files have been deleted successfully');
  51.  *     }
  52.  * });
  53.  *
  54.  * // Error Handling
  55.  * async.each(withMissingFileList, deleteFile, function(err){
  56.  *     console.log(err);
  57.  *     // [ Error: ENOENT: no such file or directory ]
  58.  *     // since dir4/file2.txt does not exist
  59.  *     // dir1/file1.txt could have been deleted
  60.  * });
  61.  *
  62.  * // Using Promises
  63.  * async.each(fileList, deleteFile)
  64.  * .then( () => {
  65.  *     console.log('All files have been deleted successfully');
  66.  * }).catch( err => {
  67.  *     console.log(err);
  68.  * });
  69.  *
  70.  * // Error Handling
  71.  * async.each(fileList, deleteFile)
  72.  * .then( () => {
  73.  *     console.log('All files have been deleted successfully');
  74.  * }).catch( err => {
  75.  *     console.log(err);
  76.  *     // [ Error: ENOENT: no such file or directory ]
  77.  *     // since dir4/file2.txt does not exist
  78.  *     // dir1/file1.txt could have been deleted
  79.  * });
  80.  *
  81.  * // Using async/await
  82.  * async () => {
  83.  *     try {
  84.  *         await async.each(files, deleteFile);
  85.  *     }
  86.  *     catch (err) {
  87.  *         console.log(err);
  88.  *     }
  89.  * }
  90.  *
  91.  * // Error Handling
  92.  * async () => {
  93.  *     try {
  94.  *         await async.each(withMissingFileList, deleteFile);
  95.  *     }
  96.  *     catch (err) {
  97.  *         console.log(err);
  98.  *         // [ Error: ENOENT: no such file or directory ]
  99.  *         // since dir4/file2.txt does not exist
  100.  *         // dir1/file1.txt could have been deleted
  101.  *     }
  102.  * }
  103.  *
  104.  */
  105. function eachLimit(coll, iteratee, callback) {
  106.     return eachOf(coll, withoutIndex(wrapAsync(iteratee)), callback);
  107. }
  109. export default awaitify(eachLimit, 3)