js Object的属性 Configurable,Enumerable,Writable,Value,Getter,Setter

对象的数据属性

Configurable,Enumerable,Writable,Value

var person = {}
Object.defineProperty(person,'name',{configurable:false,//能否使用delete、能否需改属性特性、或能否修改访问器属性、，false为不可重新定义，默认值为true enumerable:false,//对象属性是否可通过for-in循环，flase为不可循环，默认值为true writable:false,//对象属性是否可修改,flase为不可修改，默认值为true value:'xiaoming' //对象属性的默认值，默认值为undefined }); //value console.log(person);//xiaoming，默认value //writable person.name="qiang"; console.log(person);//xiaoming，不可修改value //enumerable for(var i in person){ console.log(person[i]) //无结果，不可循环 } //configurable delete person.name console.log(person.name)//xiaoming，不可删除 Object.defineProperty(person,'name',{ configurable:true //不可修改，将抛出错误 });

访问器属性

getter，setter

var book = {_year: 2004,//属性前面加_，代表属性只能通过对象方法访问edition: 0
}
Object.defineProperty(book,'year',{ get: function(){ return this._year; }, set: function(newValue){ if(newValue > 2004){ this._year = newValue; this.edition += newValue - 2004 } } }); console.log(book.year)//2004 book.year = 2006; console.log(book.year)//2006 console.log(book.edition)//2

定义多个属性

Object.defineProperties

var book = {};Object.defineProperties(book, {_year: {value:2004,writable:true},edition: {value: 0,writable:true }, year: { get: function() { return this._year; }, set: function(newValue) { if (newValue > 2004) { this._year = newValue; this.edition += newValue - 2004 } } } }); console.log(book.year) //2004 book.year = 2006; console.log(book.year) //2006 console.log(book.edition) //2

读取属性

var book = {};Object.defineProperties(book, {_year: {value:2004,writable:true},edition: {value: 0, writable:true }, year: { get: function() { return this._year; }, set: function(newValue) { if (newValue > 2004) { this._year = newValue; this.edition += newValue - 2004 } } } }); console.log(book.year) //2004 book.year = 2006; console.log(book.year) //2006 console.log(book.edition) //2 //读取属性 var descriptor__year = Object.getOwnPropertyDescriptor(book,'_year'); var descriptor_year = Object.getOwnPropertyDescriptor(book,'year');