unique的设计，jQuery源码解析（架构与依赖模块）教程-慕课网

unique的设计

Unique：确保一次只能添加一个回调(所以在列表中没有重复的回调)

function fn1(val) {
  console.log('fn1 says ' + val);
}
var callbacks = $.Callbacks( "unique" );
callbacks.add( fn1 );
callbacks.add( fn1 ); // repeat addition
callbacks.add( fn1 );
callbacks.fire( "foo" );

结果：过滤了相同的add操作

fn1 says foo

过滤重复的比较简单，因为是数组的保存方式，我们可以在入口处通过indexOf判断即可

function Callbacks(options) {
  var list = [];
  var self;
  var firingStart;
  var memory;

  function _fire(data) {
    memory = options === 'memory' && data;
    firingIndex = firingStart || 0;
    firingStart = 0;
    firingLength = list.length;
    for (; list && firingIndex < firingLength; firingIndex++) {
      list[firingIndex](data)
    }
  }

  self = {
    add: function(fn) {
      var start = list.length;
      if (options == 'unique') {
        if (-1 === list.indexOf(fn)) {
          list.push(fn)
        }
      } else {
        list.push(fn)
      }
      if (memory) {
        firingStart = start; //获取最后一值
        _fire(memory);
      }
    },
    fire: function(args) {
      if (list) {
        _fire(args)
      }
    }
  }
  return self;
}

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<script src="http://img1.sycdn.imooc.com//down/540812440001e40e00000000.js" type="text/javascript"></script>
<script src="http://img1.sycdn.imooc.com//down/541f6ff70001a0a500000000.js" type="text/javascript"></script>
<title></title>
</head>
<body>
<script type="text/javascript">
function Callbacks(options) {
var list = [];
var self;
var firingStart;
var memory;
function _fire(data) {
memory = options === 'memory' && data;
firingIndex = firingStart || 0;
firingStart = 0;
firingLength = list.length;
for (; list && firingIndex < firingLength; firingIndex++) {
list[firingIndex](data)
}
}
self = {
add: function(fn) {
var start = list.length;
if (options == 'unique') {
if (-1 === list.indexOf(fn)) {
list.push(fn)
}
} else {
list.push(fn)
}
if (memory) {
firingStart = start; //获取最后一值
_fire(memory);
}
},
fire: function(args) {
if (list) {
_fire(args)
}
}
}
return self;
}
function fn1(val) {
show('fn1 says ' + val);
}
var callbacks = Callbacks( "unique" );
callbacks.add( fn1 );
callbacks.add( fn1 ); // 重复添加
callbacks.add( fn1 );
callbacks.fire( "foo" );
</script>
</body>
</html>

unique的设计

任务