JavaScript/Notes/CustomEvents
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What are they?
An event is a function call that signifies something happened.
Data Received
Example: HSVPicker.
<source lang="javascript"> var transport = new AjaxTransport(url); transport.onsuccess = transportSuccessHandler;
function transportSuccessHandler(ev) {
var data = ev.data; updateTable(data);
} </source>
Custom calls notify subscribers. The function is either defined by the "class" (default) or shadowed on the instance, by the client of the API.
Objects Talking
- Class - defines methods and default handlers
- Instance - shadows class
- Instance usage (from other objects)
Why?
Centralized dispatch. Method called from many places and when it is done, shared notifications fire.
<source lang="javascript"> var tableSort = new Factory(function() {
function _getSortFunction(sortType) { if(sortType == "number") { return function() { }; } } function _isSortedBy(tableSort, sortType) { } var configData = {}; function TableSort(id, config) { this.id = id; configData[id] = Object.create(config); } TableSort.prototype.sortBy = function(sortType) { var config = configData[this.id]; if(config.currentSort != sortType) { config.sortFunction(this); this.onsort(sortType); } }; return TableSort;
});
function Factory(getConstructor){
var i = 0, ctor; this.getById = getById; function getById(id, config) { var instances = this.instances; if(!instances) { // First time. instances = this.instances = {}; // Get the constructor. ctor = getConstructor(this); } return instances[id] || (instances[id] = new ctor(id, config)); }
} </source>