如何检查ECMAScript 6类和函数之间的区别？ [英] How do you check the difference between an ECMAScript 6 class and function?

问题描述

在ECMAScript 6中，类的 typeof 根据规范，'function'。

In ECMAScript 6 the typeof of classes is, according to the specification, 'function'.

但是，根据规范，您不允许将通过类语法创建的对象调用为正常的函数调用。换句话说，您必须使用新的关键字，否则将抛出TypeError。

However also according to the specification you are not allowed to call the object created via the class syntax as a normal function call. In other words, you must use the new keyword otherwise a TypeError is thrown.

TypeError：类不能被函数调用

所以没有使用try catch，这将是非常丑陋和破坏性能，你怎么能检查一个函数是否来自类语法或函数语法？

So without using try catch, which would be very ugly and destroy performance, how can you check to see if a function came from the class syntax or from the function syntax?

推荐答案

我认为检查函数是否是ES6类的最简单的方法是检查 .toString（） 方法。根据 es2015规格：

I think the simplest way to check if the function is ES6 class is to check the result of .toString() method. According to the es2015 spec:

字符串表示必须具有FunctionDeclaration FunctionExpression，GeneratorDeclaration，GeneratorExpression，ClassDeclaration，ClassExpression，ArrowFunction，MethodDefinition或GeneratorMethod的语法，具体取决于实际对象的特征

The string representation must have the syntax of a FunctionDeclaration FunctionExpression, GeneratorDeclaration, GeneratorExpression, ClassDeclaration, ClassExpression, ArrowFunction, MethodDefinition, or GeneratorMethod depending upon the actual characteristics of the object

所以检查功能看起来很简单：

So the check function looks pretty simple:

function isClass(func) {
  return typeof func === 'function' 
    && /^class\s/.test(Function.prototype.toString.call(func));
}

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