jQuery1.11源码分析(10)-----Callbacks模块

Callbacks模块实质上就是一个回调函数队列(当然吹得很牛逼。。比如“提供了一种强大的方法来管理回调函数队列”)，之所以介绍它是因为后面的Derferred模块基于它。

Callbacks生成时接收四个设置:once(只触发一遍)，memory（记录前一次的触发传入参数，disable时是否清空队列）,unique(确保队列中同样的函数只有一个)，stopOnFalse（当调用某一个回调函数返回false时则停止触发）

例：jQuery.Callbacks(‘once memory‘)

Callbacks模块还有几个API，add,remove,has,empty,disable,lock,fire,fireWith(根据指定的上下文触发)，以及两个状态判断函数，locked和disabled。

这几个API的用法就像名字所述的那样，增加啊，移除啊之类的。。更多信息可以看文档

这个模块没什么难度，在编写时主要有两个点需要考虑：1，当我添加或者删除某个函数时，该队列正在触发怎么办？2，当我要触发某一个队列时，该队列正在触发怎么办？

答：记录状态，做处理即可

//因为队列可能在调用时被改变，所以需要考虑两种状态，没调用和调用时。

jQuery.Callbacks = function( options ) {

    // Convert options from String-formatted to Object-formatted if needed
    // (we check in cache first)
    //这样处理一下以后调用就可以保证options存在，不会像我option&&option.xxx
    options = typeof options === "string" ?
        ( optionsCache[ options ] || createOptions( options ) ) :
        jQuery.extend( {}, options );

    var // Flag to know if list is currently firing
        firing,
        // Last fire value (for non-forgettable lists)
        memory,
        // Flag to know if list was already fired
        fired,
        // End of the loop when firing
        firingLength,
        // Index of currently firing callback (modified by remove if needed)
        firingIndex,
        // First callback to fire (used internally by add and fireWith)
        firingStart,
        // Actual callback list
        list = [],
        // Stack of fire calls for repeatable lists
        //这里的stack存的不是fn，而是传给fn调用的arguments
        //这里名称上是stack，实际上是queue
        stack = !options.once && [],
        // Fire callbacks
        //data[0]是上下文
        //data[1]是传给各个回调函数的参数
        fire = function( data ) {
            memory = options.memory && data;
            fired = true;
            firingIndex = firingStart || 0;
            firingStart = 0;
            firingLength = list.length;
            firing = true;
            for ( ; list && firingIndex < firingLength; firingIndex++ ) {
                //当传入的data[0]为数组时，函数调用时的this依然是这个数组，而非数组中的item
                if ( list[ firingIndex ].apply( data[ 0 ], data[ 1 ] ) === false && options.stopOnFalse ) {
                    memory = false; // To prevent further calls using add
                    break;
                }
            }
            firing = false;
            //这里主要考虑在执行的过程中会再次执行，所以用stack来保存传入的参数
            if ( list ) {
                if ( stack ) {
                    if ( stack.length ) {
                        fire( stack.shift() );
                    }
                } else if ( memory ) {
                    list = [];
                } else {
                    self.disable();
                }
            }
        },
        // Actual Callbacks object
        self = {
            // Add a callback or a collection of callbacks to the list
            add: function() {
                if ( list ) {
                    // First, we save the current length
                    var start = list.length;
                    //这里用闭包函数的主要原因是要递归调用，质疑
                    (function add( args ) {
                        jQuery.each( args, function( _, arg ) {
                            console.log(‘list‘);
                            console.log(list);
                            var type = jQuery.type( arg );
                            if ( type === "function" ) {
                                if ( !options.unique || !self.has( arg ) ) {
                                    list.push( arg );
                                }
                            //当传入的参数是多维数组时递归调用，有必要这样处理吗？是后面有这种用法
                            } else if ( arg && arg.length && type !== "string" ) {
                                // Inspect recursively
                                console.log(‘递归‘);
                                add( arg );
                            }
                        });
                    })( arguments );
                    // Do we need to add the callbacks to the
                    // current firing batch?
                    if ( firing ) {
                        firingLength = list.length;
                    // With memory, if we‘re not firing then
                    // we should call right away
                    //如果有memory，但我们又不是正在触发，所以要立刻触发后面增加的函数
                    //这里可以思考一下
                    } else if ( memory ) {
                        firingStart = start;
                        fire( memory );
                    }
                }
                return this;
            },
            // Remove a callback from the list
            remove: function() {
                if ( list ) {
                    jQuery.each( arguments, function( _, arg ) {
                        var index;
                        while ( ( index = jQuery.inArray( arg, list, index ) ) > -1 ) {
                            //删除很简单就删除了
                            list.splice( index, 1 );
                            // Handle firing indexes
                            //需要考虑正在触发的情况
                            if ( firing ) {
                                if ( index <= firingLength ) {
                                    firingLength--;
                                }
                                if ( index <= firingIndex ) {
                                    firingIndex--;
                                }
                            }
                        }
                    });
                }
                return this;
            },
            // Check if a given callback is in the list.
            // If no argument is given, return whether or not list has callbacks attached.
            has: function( fn ) {
                return fn ? jQuery.inArray( fn, list ) > -1 : !!( list && list.length );
            },
            // Remove all callbacks from the list
            empty: function() {
                list = [];
                firingLength = 0;
                return this;
            },
            // Have the list do nothing anymore
            disable: function() {
                list = stack = memory = undefined;
                return this;
            },
            // Is it disabled?
            disabled: function() {
                return !list;
            },
            // Lock the list in its current state
            lock: function() {
                stack = undefined;
                if ( !memory ) {
                    self.disable();
                }
                return this;
            },
            // Is it locked?
            locked: function() {
                return !stack;
            },
            // Call all callbacks with the given context and arguments
            fireWith: function( context, args ) {
                if ( list && ( !fired || stack ) ) {
                    args = args || [];
                    args = [ context, args.slice ? args.slice() : args ];
                    if ( firing ) {
                        stack.push( args );
                    } else {
                        fire( args );
                    }
                }
                return this;
            },
            // Call all the callbacks with the given arguments
            fire: function() {
                self.fireWith( this, arguments );
                return this;
            },
            // To know if the callbacks have already been called at least once
            fired: function() {
                return !!fired;
            }
        };

    return self;
};

jQuery1.11源码分析(10)-----Callbacks模块,古老的榕树,5-wow.com