如何在 Javascript 中检查实例的类？
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How to check the class of an instance in Javascript?
提问by mko
Possible Duplicate:
How to get a JavaScript Object's Class?
可能的重复：
如何获取 JavaScript 对象的类？
In Ruby I could do this to check the class of an instance:
在 Ruby 中，我可以这样做来检查实例的类：
'this is an string'.class
=>String
Is there any similar thing in js?
js中有没有类似的东西？
回答by Nathan Wall
You probably mean type or constructor, not class. Class has a different meaning in JavaScript.
您可能指的是类型或构造函数，而不是类。类在 JavaScript 中有不同的含义。
To get the class:
获取课程：
var getClassOf = Function.prototype.call.bind(Object.prototype.toString);
getClassOf(new Date()); // => "[object Date]"
getClassOf('test string'); // => "[object String]"
getClassOf({ x: 1 }); // => "[object Object]"
getClassOf(function() { }); // => "[object Function]"
To get the constructor or prototype there are several ways, depending on what you need.
要获取构造函数或原型，有多种方法，具体取决于您的需要。
To discover what type of primitive you have, use typeof. This is the best thing to use with strings, booleans, numbers, etc:
要发现您拥有哪种类型的原语，请使用typeof. 这是与字符串、布尔值、数字等一起使用的最佳方法：
typeof 'test string'; // => 'string'
typeof 3; // => 'number'
typeof false; // => 'boolean'
typeof function() { }; // => 'function'
typeof { x: 1 }; // => 'object'
typeof undefined; // => 'undefined'
Just beware that nullacts weird in this case, as typeof nullwill give you "object", not "null".
请注意，null在这种情况下，行为很奇怪，因为typeof null会给您"object"，而不是"null".
You can also get the prototype, the backbone JavaScript inheritance, with Object.getPrototypeOf(myObject)(or myObject.__proto__or myObject.constructor.prototypein some browsers when getPrototypeOfisn't supported).
您还可以使用Object.getPrototypeOf(myObject)（myObject.__proto__或myObject.constructor.prototype在getPrototypeOf不支持的某些浏览器中）获取原型，即主干 JavaScript 继承。
You can test the constructor with instanceof:
您可以使用以下方法测试构造函数instanceof：
new Date() instanceof Date; // => true
You can also reasonably get the constructor with myObject.constructor, although be aware that this can be changed. To get the name of the constructor, use myObject.constructor.name.
您也可以使用 合理地获取构造函数myObject.constructor，但请注意这可以更改。要获取构造函数的名称，请使用myObject.constructor.name.
new Date().constructor.name; // => 'Date'
回答by KooiInc
Not sure if this goes for all browsers, but you can use constructor.name:
不确定这是否适用于所有浏览器，但您可以使用constructor.name：
'some string'.constructor.name; //=>String
({}).constructor.name //=>Object
(7.3).constructor.name //=>Number
[].constructor.name //=>Array
(function(){}).constructor.name //=>Function
true.constructor.name //=>Boolean
/test/i.constructor.name //=>RegExp
(new Date).constructor.name //=>Date
(new function MyConstructor(){}())
.constructor.name; //=>MyConstructor
Whilst Objectis the mother of all in Javascript, you could extend it (there are pros and consto it)
虽然它Object是 Javascript 之母，但您可以扩展它（它有利有弊）
Object.prototype.class = function(){
return this.constructor.name;
}
'some string'.class(); //=>String
(23).class(); //=>Number
// etc...
Note: javascript doesn't know 'classes'1, its inheritance model is prototypal
注意：javascript 不知道 'classes' 1，它的继承模型是原型
1from the ECMAScript standard.
1来自 ECMAScript 标准。
ECMAScript does not use classes such as those in C++, Smalltalk, or Java. Instead objects may be created in various ways including via a literal notation or via constructors which create objects and then execute code that initialises all or part of them by assigning initial values to their properties. Each constructor is a function that has a property named prototype that is used to implement prototype-based inheritance and shared properties. Objects are created by using constructors in new expressions; for example, new Date(2009,11) creates a new Date object. Invoking a constructor without using new has consequences that depend on the constructor. For example, Date() produces a string representation of the current date and time rather than an object.
ECMAScript 不使用诸如 C++、Smalltalk 或 Java 中的类。相反，可以通过各种方式创建对象，包括通过文字符号或通过构造函数创建对象，然后执行代码，通过将初始值分配给它们的属性来初始化它们的全部或部分。每个构造函数都是一个函数，它有一个名为prototype 的属性，用于实现基于原型的继承和共享属性。对象是通过在 new 表达式中使用构造函数创建的；例如， new Date(2009,11) 创建一个新的 Date 对象。在不使用 new 的情况下调用构造函数的后果取决于构造函数。例如，Date() 生成当前日期和时间的字符串表示而不是对象。
回答by amd
In js you can use :
在 js 中，您可以使用：
typeof
eq.
等式
var a="this is string";
typeof a; // return "string"
function abc(){}
typeof abc; // return "function"
var a = {a:1,b:2,c:3}
typeof a; return "object"
回答by Nemoden
typeofand instanceofis what you need
typeof并且instanceof是你所需要的
> x = "Hello, World!"
"Hello, World!"
> typeof x
"string"
You can check constructors name to get a name of constructors class (or that what you call a class):
您可以检查构造函数名称以获取构造函数类的名称（或您称之为类的名称）：
> x.constructor.name
> "String"
