JavaScript Core chapter 十 _JavaScript

JavaScript Core chapter 10

一些基础概念：

#1 JavaScript 对象其实就是属性的集合。属性由键值对组成。通过[属性名]这种形式则总是可以保证正确性。

#2 函数：?函数本身也是对象。

function func(id){};

相当于：

var func = function(id){};

#3?this?表示当前上下文，即调用者的引用。

#4 词法作用域?即是在定义的时候就确定下来了。

#5 scope?在执行一个函数时，函数的参数和其局部变量会作为调用对象的属性进行存储

#6 call & apply

#7 ?由于构造函数定义了一个对象的类，所以属性constructor在有助于确定给定对象的类型．如，可以使用如下代码来确定一个未知对象的类型：if ((typeof o == "object") && (o.constructor == Date)),也可以用instanceof运算符：if ((typeof o == "object") && (o instanceof Date))

#8?对象的引用机制：对象不会被复制，只能通过引用来传递。

var recordDefParams = [];

recordDefParams[0] = {name:'id',type:'date'};
recordDefParams[1] = {name:'version'};
recordDefParams[recordDefParams.length] = {name:'deleted'};
function func(recordDefParams){
    for (var i = 0, nLen = recordDefParams.length; i < nLen; i++) {
        var obj = recordDefParams[i];
        if (obj.type == 'date' && !obj.dateFormat) {
            obj.dateFormat = 'xxx-xx-x';
        }
    }
    return recordDefParams;
}
console.dir(recordDefParams);
console.log('===========================');
console.dir(func(recordDefParams));

function addr(street, xno){
    console.log(this);
    this.street = street || 'beijinglu';
    this.xno = xno || '1 hao';
    this.toString = function(){
        return 'Street:' + this.street + ' xno:' + this.xno;
    };
};
var core1 = new addr();
console.log(core1.toString());
var core2 = new addr('北京路','一号');
console.log(core2.toString());

//动态构建新的匿名对象
function point(x,y){
    this.x = x;
    this.y = y;
    return {'x':x,'y':y};
}
var a = point(3,4);
console.dir(a);
for(var key in a ){
   console.log(key);
   console.log(a[key]);
}

After read the blog of "JavaScript Core chapter 10 .writer the coding below for testing.

<html>
	<head>
		<title>
			 Js core
		</title>
		<script type="text/javascript">
			//原型链
			var base = {
				name : 'Mark',
				getName : function(){
					return this.name;
				}
			};
			var ext1 ={
				id :'0',
				__proto__ :base
			};
			var ext2 ={
				id : '9',
				__proto__ : base
			};
			//console.log(ext1.getName());
			
			//构造器
			function Task(id){
				this.id = id;
			};
			Task.prototype.status = 'defalt_begin';
			Task.prototype.execute = function(args){
				return 'execute task_[' + this.id + ']' + this.status + ':' + args;
			};
			var task1 = new Task(1);
			var task2 = new Task(2);
			task1.status = 'activing';
			task2.status = 'end...';
			//console.log(task1.execute('task_1'));
			//console.log(task2.execute('task_2'));
			
			//this understander
			var global = this;
			var tom = {
				name : 'tom',
				id : '1',
				getInfo: function(){
					console.log(this.name + ':' + this.id);
				}
			}
			var jetty = {
				name : 'jetty',
				getInfo : tom.getInfo 
				//等同于
				//getInfo:function (){ console.log(this.name + ':' + this.id);} 在跑构造的时候就创建好了。
			}
			
			tom.getInfo();
			jetty.getInfo();
			global.getInfo = tom.getInfo;
			global.getInfo();
		</script>
	</head>
	<body>
		 js core chapter 10 & 11.
	</body>
</html>

? ?all : 给全局对象动态的添加一个属性。