1 files changed, 77 insertions, 0 deletions
diff --git a/extensions/fastdom-promised.js b/extensions/fastdom-promised.js
new file mode 100644
index 0000000..e002072
--- /dev/null
+++ b/extensions/fastdom-promised.js
@@ -0,0 +1,77 @@
+!(function() {
+
+/**
+ * Wraps fastdom in a Promise API
+ * for improved control-flow.
+ *
+ * @example
+ *
+ * // returning a result
+ * fastdom.measure(() => el.clientWidth)
+ *   .then(result => ...);
+ *
+ * // returning promises from tasks
+ * fastdom.measure(() => {
+ *   var w = el1.clientWidth;
+ *   return fastdom.mutate(() => el2.style.width = w + 'px');
+ * }).then(() => console.log('all done'));
+ *
+ * // clearing pending tasks
+ * var promise = fastdom.measure(...)
+ * fastdom.clear(promise);
+ *
+ * @type {Object}
+ */
+var exports = {
+  initialize: function() {
+    this._tasks = new Map();
+  },
+
+  mutate: function(fn, ctx) {
+    return create(this, 'mutate', fn, ctx);
+  },
+
+  measure: function(fn, ctx) {
+    return create(this, 'measure', fn, ctx);
+  },
+
+  clear: function(promise) {
+    var tasks = this._tasks;
+    var task = tasks.get(promise);
+    this.fastdom.clear(task);
+    tasks.delete(task);
+  }
+};
+
+/**
+ * Create a fastdom task wrapped in
+ * a 'cancellable' Promise.
+ *
+ * @param  {FastDom}  fastdom
+ * @param  {String}   type - 'measure'|'muatate'
+ * @param  {Function} fn
+ * @return {Promise}
+ */
+function create(promised, type, fn, ctx) {
+  var tasks = promised._tasks;
+  var fastdom = promised.fastdom;
+  var task;
+
+  var promise = new Promise(function(resolve, reject) {
+    task = fastdom[type](function() {
+      tasks.delete(promise);
+      try { resolve(fn()); }
+      catch (e) { reject(e); }
+    }, ctx);
+  });
+
+  tasks.set(promise, task);
+  return promise;
+}
+
+// Expose to CJS, AMD or global
+if ((typeof define)[0] == 'f') define(function() { return exports; });
+else if ((typeof module)[0] == 'o') module.exports = exports;
+else window.fastdomPromised = exports;
+
+})();
+\ No newline at end of file