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javascript变量,作用域和内存问题(一)

2024-04-27 14:11:48
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javascript变量,作用域和内存问题(一)

js对象的引用是很有意思的,引用型对象是不可以直接引用的,我猜测这是原型的来源之一,有大神请详解或斧正。“引用类型的值是保存在内存中的对象。与其他语言不同,Javascript不允许直接访问内存中的位置,也就是说不能直接操作对象的内存空间。在操作对象时,实际上是在操作对象的引用而不是实际的对象。为此,引用类型的值是按引用访问的。 在很多语言中,字符串以对象的形式来表示,因此被认为是引用类型的。ECMAScript放弃了这一传统。”(from《js高级程序设计》) 一.动态的属性 我们可以这样写:
var person = new Object();person.name = "Nicholas";//"Nicholas"alert(person.name);但是,我们不能这样写:var name = "Nicholas";name.age = 27;//undefinedalert(name.age);
这是因为,我们只能给引用类型的值添加属性,而不能给基本类型的值添加属性。 二.复制值基本类型是直接复制,而引用类型是复制一个指针指向原来的值,并且此时会分配空间,改变一个值同时也会改变另外一个值,包括属性等。 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