JavaScript Es6 在内部函数中引用 this？

Question

Es6 classes this always refers to the object in which it was created in, even inside an inner function because it does var _this = this and any reference to this will become _this . However what if I need want to reference the context of an inner function within that class?

class Body {
    constructor () {
        Hooks.subscribe('', () => {
            // I want this to reference the context that is within this method
            // elsewhere because bind,apply,call sets new context
        })
    }
}

How can I refer to the context of Hooks.subscribe inside an es6 class?

Answer 1

Assuming you want to reference Hooks's this :

And also assuming that the subscribe function returns the original hook object

You can do:

class Body {
    constructor () {
        const hook = Hooks.subscribe('', () => {
            // `this` will still reference `Body`'s objects this
            // `hook` will reference the hook object
        });
    }
}

Answer 2

Because you are using an arrow function this is kept in scope from the parent. To reassign this to current scope, remove the arrow function.

class Body {
    constructor () {
        Hooks.subscribe('', function() {
            // `this` is now the context of Hooks.subscribe
        });
    }
}