方法销毁无效

Question

Trying to determine why this wont function properly.

// assuming this works
const { emitter } = window.project;
emitter.emit('foo');

// why doesnt this
const { emitter: { emit } } = window.project;
emit('foo');

Answer 1

Presumably because the emit method depends on this referring to a specific value. The value of this depends on how a function is called (if it's an unbound, non-arrow function), and you are calling the function in two different ways:

• emitter.emit() will cause this inside emit to refer to emitter
• emit() will cause this to refer to undefined (strict mode) or the global object (non-strict mode)

That has nothing to do with ES6 specifically.

More information about this : You Don't Know JS: this & Object Prototypes .