JavaScript组合模式学习要点

//定义组合对象
var Folder = function (name) {
this.name = name;
this.parent = null;
this.files = [];
};
Folder.prototype.add = function (file) {
file.parent = this;
if(this.files.indexOf(file) === -1){
this.files.push(file);
}else{
console.log('\''+file.name+'\'已存在,添加失败');
}
};
Folder.prototype.scan = function () {
if(this.parent){
console.log('开始扫描\''+this.parent.name+'\': '+this.name);
}else{
console.log('开始扫描根目录: '+this.name);
}
//关键在这里，调用所有它的叶对象的接口方法scan()
for(var i = 0, file; file = this.files[i++];){
file.scan();
}
};
Folder.prototype.remove = function (file) {
var n = this.files.indexOf(file);
if(n === -1){console.log('无法删除: \''+file.name+'\'不存在:');}
if(n >= 0){
this.files.splice(n,1);
console.log('成功删除:'+file.name);
}
};
//定义叶对象
var File = function (name) {
this.name = name;
this.parent = null;
};
File.prototype.add = function () {
console.log('不能添加在文件下面');
};
File.prototype.scan = function () {
console.log(this.parent.name+': '+this.name);
};
File.prototype.remove = function (file) {
console.log('无法删除: \''+file.name+'\'不存在:');
};
//测试
var folder = new Folder('目录');
var folder1 = new Folder('学习质料');
var folder2 = new Folder('javascript');
var file1 = new File('Node.js');
var file2 = new File('qq.jpg');
folder.add(folder1);
folder.add(folder1);
folder.add(folder2);
folder1.add(file1);
folder2.add(file2);
//'学习质料'添加成功
//'学习质料'已存在,添加失败
//'javascript'添加成功
//'Node.js'添加成功
//'qq.jpg'添加成功
folder.remove(folder1);
folder.remove(folder1);
file1.remove(file1);
//成功删除:学习质料
//无法删除: '学习质料'不存在:
//无法删除: 'Node.js'不存在:
folder.scan(); //这里相当于执行了一个宏命令
//开始扫描根目录: 目录
//开始扫描'目录': javascript
//javascript: qq.jpg