[js] OO(面向对象) 属性
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1 <!DOCTYPE html> 2 <html> 3 4 <head> 5 <meta charset="UTF-8"> 6 <title></title> 7 </head> 8 9 <body> 10 <script> 11 /* 12 * 数据属性 13 */ 14 var person = {}; 15 Object.defineProperty(person, "name", { 16 writable: true, //能否修改属性的值 17 configurable: true, //能否删除(delete)属性，一旦设置为false，不可更改 18 enumberable: true, //能否for-in 循环返回属性 19 value: "Nicholas" //设置属性的值,默认 undefined 20 }); 21 console.log(person.name); 22 person.name = "Michael"; 23 console.log(person.name); 24 /* 25 * 访问器属性 26 */ 27 var book = { 28 _year: 2004, 29 edition: 1 30 }; 31 Object.defineProperty(book, "year", { 32 get: function() { 33 return this._year; 34 }, //读取属性时调用的函数 35 set: function(newValue) { 36 if (newValue > 2004) { 37 this._year = newValue; 38 this.edition += newValue - 2004; 39 } 40 } //写入属性时调用的函数 41 }); 42 book.year = 2005; 43 console.log(book._year); 44 console.log(book.edition); //2 45 /* 46 * defineProperties写法 47 */ 48 var book = {}; 49 Object.defineProperties(book, { 50 _year: { 51 writable: true, //此时必须指定 52 value: 2004 53 }, 54 edition: { 55 writable: true, //此时必须指定 56 value: 1 57 }, 58 year: { 59 get: function() { 60 return this._year; 61 }, 62 set: function(newValue) { 63 if (newValue > 2004) { 64 this._year = newValue; 65 this.edition += newValue - 2004; 66 } 67 } 68 } 69 }); 70 book.year = 2005; 71 console.log(book._year); 72 console.log(book.edition); //2 73 /* 74 * 读取属性特性 75 */ 76 var book = {}; 77 Object.defineProperties(book, { 78 _year: { 79 value: 2004 80 }, 81 edition: { 82 value: 1 83 }, 84 year: { 85 get: function() { 86 return this._year; 87 }, 88 set: function(newValue) { 89 if (newValue > 2004) { 90 this._year = newValue; 91 this.edition += newValue - 2004; 92 } 93 } 94 } 95 }); 96 var descriptor = Object.getOwnPropertyDescriptor(book, "_year"); 97 console.log(descriptor.value); //2004 98 console.log(descriptor.configurable); //false,不设置的话默认false 99 console.log(typeof descriptor.get); //"undefined" 100 var descriptor = Object.getOwnPropertyDescriptor(book, "year"); 101 console.log(descriptor.value); //undefined 102 console.log(descriptor.enumerable); //false,不设置的话默认false 103 console.log(typeof descriptor.get); //"function" 104 </script> 105 </body> 106 107 </html>
一般来说，对象的属性 用 _xx 形式写。
