JavaScript类型系统之Object详解

var person = new Object();
//如果不给构造函数传递参数可以不加括号 var person = new Object;
person.name = 'bai';
person.age = 29; 
//创建无属性的空对象
var cody1 = new Object();
var cody2 = new Object(undefined);
var cody3 = new Object(null);
console.log(typeof cody1,typeof cody2, typeof cody3);//object object object 
//创建string、number、array、function、boolean、regex
console.log(new Object('foo'));
console.log(new Object(1));
console.log(new Object([]));
console.log(new Object(function(){}));
console.log(new Object(true));
console.log(new Object(/\bbt[a-z]+\b/));

var person = {
name : 'bai',
age : 29,
5 : true
};

//同上
var person = {
'name' : 'bai',
'age' : 29,
'5' : true
};

//等价于var person = new Object();
var person = {}; 
[tips]使用对象字面量封装多个可选参数
function displayInfo(args){
var output = '';
if(typeof args.name == 'string'){
output += 'name:' + args.name +'\n';
}
if(typeof args.age == 'number'){
output += 'Age:' + args.age + '\n';
}
console.log(output);
};
displayInfo({
name: 'Nicholas',
age: 29
});
displayInfo({
name: 'match'
});

var myObject = {
123:'zero',
class:'foo'
};
console.log(myObject['123'],myObject['class']);//'zero' 'foo'
console.log(myObject.123);//报错

person[0] = 1; //[]中的数字不会报错，而是自动转换成字符串
person[a] = 1; //[]中符合变量命名规则的元素会被当成变量，变量未被定义，而报错
person[''] = 2; //[]中的空字符串不会报错,是实际存在的且可以调用,但不会在控制台右侧的集合中显示
person[undefined 或 null 或 true 或 false] = 4;// 不会报错，而是自动转换成字符串
person['白'] = 6; // 不会报错 

var foo = {bar: 'bar'};
delete foo.bar;
console.log('bar' in foo);//false 
var a = 123;
delete a;
console.log(a);//123

var a;
a = 10;
console.log(a,window.a);//10 10
window.a = 20;
console.log(a,window.a);//20 20
delete a ;
console.log(a,window.a);//20 20
delete window.a;
console.log(a,window.a);//20 20

window.b = 10;
console.log(b,window.b);//10 10
delete b;
console.log(b);//报错
console.log(window.b);//undefined 
window.b = 10;
console.log(b,window.b);//10 10
delete window.b;
console.log(b);//报错
console.log(window.b);//undefined 

var student = {
name : {
chinese : 1,
englisth : 2
},
sex : 1,
age : 26
}

var object1 = {
object1_1:{
object1_1_1:{foo: 'bar'},
object1_1_2:{}
},
object1_2:{
object1_2_1:{},
object1_2_2:{}
}
};
console.log(object1.object1_1.object1_1_1.foo);//bar

var myObject = {
mark: true
};
console.log(myObject.constructor);//function Object(){}
console.log(myObject.hasOwnProperty('mark'));//true
console.log(Object.prototype.isPrototypeOf(myObject));//true
console.log(myObject.propertyIsEnumerable('mark'));//true
console.log(myObject.toLocaleString());//[object Object]
console.log(myObject.toString());//[object Object]
console.log(typeof myObject.valueOf(),myObject.valueOf());// object Object{mark:true}

var o = new Object();