[JavaScript知识库]javascript高级程序设计阅读收获（8.4.2）——类定义

1.函数申明可以提升，类定义不能提升

console.log(FunctionExpression);//undefined
var FunctionExpression = function(){};
console.log(FunctionExpression);//? (){}

console.log(FunctionDeclaration);//? FunctionDeclaration(){}
function FunctionDeclaration(){};
console.log(FunctionDeclaration);//? FunctionDeclaration(){}

console.log(ClassExpression);//undefined
var ClassExpression = class{};
console.log(ClassExpression);//calss{}

console.log(ClassDeclaration);//ReferenceError:ClassDeclaration is not defined
class Classdeclaration{};
console.log(ClassDeclaration);//class ClassDeclaration{}

2.函数受函数作用域限制，而类受块作用域限制

{
	function FunctionDeclaration(){}
	class ClassDeclaration{}
}
console.log(FunctionDeclaration);//? FunctionDeclaration(){}
console.log(ClassDeclaration);//ReferenceError: ClassDeclaration is not defined

3.类表达式的名称是可选的。在把类表达式赋值给变量后，可以通过name属性来取得类表达式的名称字符串。但不能在类表达式作用域外部访问这个标识符。

let Person = Class PersonName{
	identify(){
		console.log(Person.name,PersonName.name);//
	}
}

let p = new Person();
p.identify();//PersonName,PersonName;
console.log(PersonName);//ReferenceError: PersonName is not defined