source: [view]
dojo.provide("dojox.NodeList.delegate");
dojo.require("dojo.NodeList-traverse");
dojo.extend(dojo.NodeList, {
delegate: function(/*String*/ selector, /*String*/ eventName, /*Function*/ fn){
// summary:
// Monitor nodes in this NodeList for [bubbled] events on nodes that match selector.
// Calls fn(evt) for those events, where (inside of fn()), this == the node
// that matches the selector.
// description:
// Sets up event handlers that can catch events on any subnodes matching a given selector,
// including nodes created after delegate() has been called.
//
// This allows an app to setup a single event handler on a high level node, rather than many
// event handlers on subnodes. For example, one onclick handler for a Tree widget, rather than separate
// handlers for each node in the tree.
// Since setting up many event handlers is expensive, this can increase performance.
//
// Note that delegate() will not work for events that don't bubble, like focus.
// onmouseenter/onmouseleave also don't currently work.
// selector:
// CSS selector valid to `dojo.query`, like ".foo" or "div > span". The
// selector is relative to the nodes in this NodeList, not the document root.
// For example myNodeList.delegate("> a", "onclick", ...) will catch events on
// anchor nodes which are (immediate) children of the nodes in myNodeList.
// eventName:
// Standard event name used as an argument to `dojo.connect`, like "onclick".
// fn:
// Callback function passed the event object, and where this == the node that matches the selector.
// That means that for example, after setting up a handler via
// dojo.query("body").delegate("fieldset", "onclick", ...)
// clicking on a fieldset or *any nodes inside of a fieldset* will be reported
// as a click on the fieldset itself.
// example:
// | dojo.query("navbar").delegate("a", "onclick", function(evt){
// | console.log("user clicked anchor ", this.node);
// | });
// Possible future tasks:
// - change signature of callback to be fn(node, evt), and then have scope argument
// to delegate(selector, eventName, scope, fn)?
// - support non-bubbling events like focus
// - support onmouseenter/onmouseleave
// - maybe should return an array of connect handles instead, to allow undelegate()?
// - single node version
return this.connect(eventName, function(evt){
var closest = dojo.query(evt.target).closest(selector, this);
if(closest.length){
fn.call(closest[0], evt);
}
}); //dojo.NodeList