util-events.js-优快云博客

本文介绍了如何使用JavaScript实现基本的事件支持功能，包括事件绑定、移除和触发。通过seajs.on、seajs.off和seajs.emit方法，开发者可以轻松地在网页应用中添加事件处理逻辑。

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/**
 * util-events.js - The minimal events support
 */
 

var events = data.events = {}
 
// Bind event

seajs.on = function(name, callback) {
  var list = events[name] || (events[name] = [])
  list.push(callback)
  return seajs
}
 
// Remove event. If `callback` is undefined, remove all callbacks for the
// event. If `event` and `callback` are both undefined, remove all callbacks
// for all events

seajs.off = function(name, callback) {
  // Remove *all* events
  if (!(name || callback)) {
    events = data.events = {}
    return seajs
  }
 
  var list = events[name]
  if (list) {
    if (callback) {
      for (var i = list.length - 1; i >= 0; i--) {
        if (list[i] === callback) {
          list.splice(i, 1)
        }
      }
    }
    else {
      delete events[name]
    }
  }
 
  return seajs
}
 
// Emit event, firing all bound callbacks. Callbacks receive the same
// arguments as `emit` does, apart from the event name

var emit = seajs.emit = function(name, data) {
  var list = events[name], fn
 
  if (list) {
    // Copy callback lists to prevent modification
    list = list.slice()
 
    // Execute event callbacks, use index because it's the faster.
    for(var i = 0, len = list.length; i < len; i++) {
      list[i](data)
    }
  }
 
  return seajs
}