1 files changed, 107 insertions, 15 deletions
diff --git a/lib/transform.js b/lib/transform.js
index 786f5d3..d2aa29e 100644
--- a/lib/transform.js
+++ b/lib/transform.js
@@ -25,26 +25,118 @@ import { promiseCallback, PROMISE_SYMBOL } from './internal/promiseCallback';
  * @returns {Promise} a promise, if no callback provided
  * @example
  *
- * async.transform([1,2,3], function(acc, item, index, callback) {
- *     // pointless async:
- *     process.nextTick(function() {
- *         acc[index] = item * 2
- *         callback(null)
+ * // file1.txt is a file that is 1000 bytes in size
+ * // file2.txt is a file that is 2000 bytes in size
+ * // file3.txt is a file that is 3000 bytes in size
+ *
+ * // helper function that returns human-readable size format from bytes
+ * function formatBytes(bytes, decimals = 2) {
+ *   // implementation not included for brevity
+ *   return humanReadbleFilesize;
+ * }
+ *
+ * const fileList = ['file1.txt','file2.txt','file3.txt'];
+ *
+ * // asynchronous function that returns the file size, transformed to human-readable format
+ * // e.g. 1024 bytes = 1KB, 1234 bytes = 1.21 KB, 1048576 bytes = 1MB, etc.
+ * function transformFileSize(acc, value, key, callback) {
+ *     fs.stat(value, function(err, stat) {
+ *         if (err) {
+ *             return callback(err);
+ *         }
+ *         acc[key] = formatBytes(stat.size);
+ *         callback(null);
  *     });
- * }, function(err, result) {
- *     // result is now equal to [2, 4, 6]
+ * }
+ *
+ * // Using callbacks
+ * async.transform(fileList, transformFileSize, function(err, result) {
+ *     if(err) {
+ *         console.log(err);
+ *     } else {
+ *         console.log(result);
+ *         // [ '1000 Bytes', '1.95 KB', '2.93 KB' ]
+ *     }
  * });
  *
+ * // Using Promises
+ * async.transform(fileList, transformFileSize)
+ * .then(result => {
+ *     console.log(result);
+ *     // [ '1000 Bytes', '1.95 KB', '2.93 KB' ]
+ * }).catch(err => {
+ *     console.log(err);
+ * });
+ *
+ * // Using async/await
+ * (async () => {
+ *     try {
+ *         let result = await async.transform(fileList, transformFileSize);
+ *         console.log(result);
+ *         // [ '1000 Bytes', '1.95 KB', '2.93 KB' ]
+ *     }
+ *     catch (err) {
+ *         console.log(err);
+ *     }
+ * })();
+ *
  * @example
  *
- * async.transform({a: 1, b: 2, c: 3}, function (obj, val, key, callback) {
- *     setImmediate(function () {
- *         obj[key] = val * 2;
- *         callback();
- *     })
- * }, function (err, result) {
- *     // result is equal to {a: 2, b: 4, c: 6}
- * })
+ * // file1.txt is a file that is 1000 bytes in size
+ * // file2.txt is a file that is 2000 bytes in size
+ * // file3.txt is a file that is 3000 bytes in size
+ *
+ * // helper function that returns human-readable size format from bytes
+ * function formatBytes(bytes, decimals = 2) {
+ *   // implementation not included for brevity
+ *   return humanReadbleFilesize;
+ * }
+ *
+ * const fileMap = { f1: 'file1.txt', f2: 'file2.txt', f3: 'file3.txt' };
+ *
+ * // asynchronous function that returns the file size, transformed to human-readable format
+ * // e.g. 1024 bytes = 1KB, 1234 bytes = 1.21 KB, 1048576 bytes = 1MB, etc.
+ * function transformFileSize(acc, value, key, callback) {
+ *     fs.stat(value, function(err, stat) {
+ *         if (err) {
+ *             return callback(err);
+ *         }
+ *         acc[key] = formatBytes(stat.size);
+ *         callback(null);
+ *     });
+ * }
+ *
+ * // Using callbacks
+ * async.transform(fileMap, transformFileSize, function(err, result) {
+ *     if(err) {
+ *         console.log(err);
+ *     } else {
+ *         console.log(result);
+ *         // { f1: '1000 Bytes', f2: '1.95 KB', f3: '2.93 KB' }
+ *     }
+ * });
+ *
+ * // Using Promises
+ * async.transform(fileMap, transformFileSize)
+ * .then(result => {
+ *     console.log(result);
+ *     // { f1: '1000 Bytes', f2: '1.95 KB', f3: '2.93 KB' }
+ * }).catch(err => {
+ *     console.log(err);
+ * });
+ *
+ * // Using async/await
+ * async () => {
+ *     try {
+ *         let result = await async.transform(fileMap, transformFileSize);
+ *         console.log(result);
+ *         // { f1: '1000 Bytes', f2: '1.95 KB', f3: '2.93 KB' }
+ *     }
+ *     catch (err) {
+ *         console.log(err);
+ *     }
+ * }
+ *
  */
 export default function transform (coll, accumulator, iteratee, callback) {
     if (arguments.length <= 3 && typeof accumulator === 'function') {