我们可以删除 ES6 类吗？

Question

Can we really delete a class create by es6 "class"?

 class myClass{} delete myClass; console.log(myClass); //output: class myClass{} var myClass=0; //Uncaught SyntaxError: Identifier 'myClass' has already been declared

Answer 1

删除只会删除对象属性或全局变量。

Answer 2

https://stackoverflow.com/a/44694753/461412

this answer is useful. yet not perfect.

i guess you could never delete it after it's declared as an identifier, but you could wrap it into a deletable variable in the first place.

still i'm looking for a better solution. our team is trying to build a detachable modules system. deadly, any declared class is not detachable. we don't like the idea of transpiling every module we load.

Answer 3

This is what I used:

window.MyClass = class extends SuperClass {} // in an external file

// load the file into a script tag, append it to the body, and execute the following after it loads:

alert(MyClass); // Outputs the class

delete window.MyClass;

alert(MyClass); // Outputs Uncaught ReferenceError: MyClass is not defined

It works fairly well. Using this approach I can import .js files into my document using script tags, access the code from the window object, and then remove the script tag and remove the reference to the class. I haven't done much testing on it, but it could be used to load custom logic for a single level in a game and then get rid of it, or something more useful perhaps. Honestly, it feels really hacky to do this.

Answer 4

This is the closest I could get to "remove" a Constructor

class MyClass { 
  constructor(a, b) {
    this.a = a;
  }
}

MyClass = null;            
console.log( MyClass );                   // -> null

var testObj = new MyClass_("val");        // -> TypeError

This does NOT delete the Constructor, it just changes the value of "MyClass" to null!

But for debugging purposes that'll do

Answer 5

I've made a worker for resolving the deletion of import classes.

worker.js

onmessage = function(e) {
    let v = JSON.parse(e.data)
    ...
    import(`module.js?p=${v.query}`)
        .then(module => {
             let obj = new module.default(v.params)
             ...
             postMessage(obj.result)
        })

main.js

async function doInBackground(x,y, output) {
    let r = await new Promise((resolve, reject) => {

        let w = new Worker('worker.js')
        w.postMessage(JSON.stringify({
            "x" : x,
            "y" : y
        }))
        w.onmessage = function(e) {
            resolve(e.data)
            delete w
        }
        w.onerror = reject
    })
    output.result = r
}