通过for…in语法可以遍历一个对象
var obj = {};
for (var i = 0; i < 10; i++) {obj[i] = i * 2;
}
for(var key in obj) {console.log(key + "==" + obj[key]);
}
function fun() { this.name = 'mm';
}
var obj = new fun();
console.log(obj.name); // mm
delete obj.name;
console.log(obj.name); // undefined
基本类型又叫做值类型,复杂类型又叫做引用类型
值类型:简单数据类型,基本数据类型,在存储时,变量中存储的是值本身,因此叫做值类型。
引用类型:复杂数据类型,在存储是,变量中存储的仅仅是地址(引用),因此叫做引用数据类型。
堆和栈
堆栈空间分配区别:
一般
由程序员分配释放, 若程序员不释放,由垃圾回收机制回收,分配方式倒是类似于链表。
// 下面代码输出的结果
function Person(name,age,salary) {this.name = name;this.age = age;this.salary = salary;
}
function f1(person) {person.name = "ls";person = new Person("aa",18,10);
}var p = new Person("zs",18,1000);
console.log(p.name);
f1(p);
console.log(p.name);
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>$永远的24k纯帅$</title><script>function Person(name,age,salary){this.name=name;this.age=age;this.salary=salary;}function f1(person) {person.name="娃哈哈";person=new Person("李美丽","12","5000");}var p=new Person("油篓口","16","6000");console.log("名字是:"+p.name);f1 (p);console.log("名字是:"+p.name)</script>
</head>
<body></body>
</html>
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>$永远的24k纯帅$</title><script>var num1 = 10;var num2 = num1;num1 = 20;console.log(num1);//20console.log(num2);//10var num = 50;function f1(num) {num = 60;console.log(num);//60}f1(num);console.log(num);//50var num1 = 55;var num2 = 66;function f1(num, num1) {num = 100;num1 = 100;num2 = 100;console.log(num);//100console.log(num1);//100console.log(num2);//100}f1(num1, num2);console.log(num1);//55console.log(num2);//100console.log(num);// 报错</script>
</head>
<body></body>
</html>
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