Upgrade to ExtJS 4.0.0 - Released 04/26/2011

[extjs.git] / src / core / src / util / DelayedTask.js

diff --git a/src/core/src/util/DelayedTask.js b/src/core/src/util/DelayedTask.js
new file mode 100644 (file)
index 0000000..41a1efb
--- /dev/null
+++ b/src/core/src/util/DelayedTask.js
@@ -0,0 +1,71 @@
+/**
+ * @class Ext.util.DelayedTask
+ * 
+ * The DelayedTask class provides a convenient way to "buffer" the execution of a method,
+ * performing setTimeout where a new timeout cancels the old timeout. When called, the
+ * task will wait the specified time period before executing. If durng that time period,
+ * the task is called again, the original call will be cancelled. This continues so that
+ * the function is only called a single time for each iteration.
+ * 
+ * This method is especially useful for things like detecting whether a user has finished
+ * typing in a text field. An example would be performing validation on a keypress. You can
+ * use this class to buffer the keypress events for a certain number of milliseconds, and
+ * perform only if they stop for that amount of time.  
+ * 
+ * ## Usage
+ * 
+ *     var task = new Ext.util.DelayedTask(function(){
+ *         alert(Ext.getDom('myInputField').value.length);
+ *     });
+ *     
+ *     // Wait 500ms before calling our function. If the user presses another key
+ *     // during that 500ms, it will be cancelled and we'll wait another 500ms.
+ *     Ext.get('myInputField').on('keypress', function(){
+ *         task.{@link #delay}(500);
+ *     });
+ * 
+ * Note that we are using a DelayedTask here to illustrate a point. The configuration
+ * option `buffer` for {@link Ext.util.Observable#addListener addListener/on} will
+ * also setup a delayed task for you to buffer events.
+ * 
+ * @constructor The parameters to this constructor serve as defaults and are not required.
+ * @param {Function} fn (optional) The default function to call.
+ * @param {Object} scope The default scope (The <code><b>this</b></code> reference) in which the
+ * function is called. If not specified, <code>this</code> will refer to the browser window.
+ * @param {Array} args (optional) The default Array of arguments.
+ */
+Ext.util.DelayedTask = function(fn, scope, args) {
+    var me = this,
+        id,
+        call = function() {
+            clearInterval(id);
+            id = null;
+            fn.apply(scope, args || []);
+        };
+
+    /**
+     * Cancels any pending timeout and queues a new one
+     * @param {Number} delay The milliseconds to delay
+     * @param {Function} newFn (optional) Overrides function passed to constructor
+     * @param {Object} newScope (optional) Overrides scope passed to constructor. Remember that if no scope
+     * is specified, <code>this</code> will refer to the browser window.
+     * @param {Array} newArgs (optional) Overrides args passed to constructor
+     */
+    this.delay = function(delay, newFn, newScope, newArgs) {
+        me.cancel();
+        fn = newFn || fn;
+        scope = newScope || scope;
+        args = newArgs || args;
+        id = setInterval(call, delay);
+    };
+
+    /**
+     * Cancel the last queued timeout
+     */
+    this.cancel = function(){
+        if (id) {
+            clearInterval(id);
+            id = null;
+        }
+    };
+};
\ No newline at end of file