确定给定名称的类是否存在 [英] Determine if class of given name exists

问题描述

这可能是一个愚蠢的问题，但是我四处搜寻却一无所获.

This may be a silly question but I've searched around and found nothing.

我有一个代码:

class A {}

let className = 'A';

我需要检查className是否对应于现有的类.

I need to check if className corresponds to an existing class.

这都不在全局范围内，并且正在node.js中运行，所以我不能使用window

This is all not in the global scope and is running in node.js so I can't use window

我知道以下方法会起作用:

I know that the following would work:

eval(`typeof ${className} === 'function'`);

但是我有点不愿意使用eval(而且小人也抱怨它)

However I am a bit reluctant to use eval (and also the linter complains about it)

此外，我还需要将类实例化为变量，再次可以使用eval进行操作，如下所示:

In addition I need to also instantiate the class as a variable which again I can do with eval like so:

 let ctor = eval(className);
 let object = new ctor();

但这又使用了eval.

But again this uses eval.

还有其他方法可以实现这些目标吗?

Is there any alternative way to achieve these?

推荐答案

使用Function构造函数

function ac(){} //new class
var f = new Function( "return typeof ac == 'function'" ) //define function to verify
f(); //returns true if class exists in the current scope

使其更通用

function ac(){} //new class
var f = function( className ){
  return new Function( "return typeof " + className + " == 'function'" )(); //define function to verify and invoke the same
} 
f( "ac" ); //returns true if class exists in the current scope

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