1.查询和设置:
for in遍历属性名;
for (propName in obj) {
console.log(propName);
console.log(obj[propName]);
}
2.删除属性:
(1).delete在什么都没执行的情况和成功的情况下返回true
o = {x:1};
//成功删除
delete o.x;
//没有意义返回true
delete o.x;
//删除继承的属性,没有执行 true
delete o.toString;
//无意义, true
delete 1;
(2). 在不能删除的情况下返回false:
//不能删除不可配置的属性
delete Object.prototype;
//不能删除声明的全局变量(var声明)和方法
var x = 1;
function f(){};
delete this.x;
delete this.f;
(3).不使用var声明的全局属性视为可配置的可以用delete删除
//等同this.x = 1
x = 1;
delete x;
3.检测属性
(1). in检测:
var o = {};
"toString" in o; //true
(2). hasOwnProperty:检测自有属性
o.hasOwnProperty("toString"); //false
(3). propertyIsEnumerable:检测自有并且可枚举的属性
(4). !==判断
o.toString !== undefined;