4castle pointet out，你可以使用计算对象属性名称和解构以及用于解构的附加键/值对变量。

As 4castle pointet out, you could use Computed object property names and destructuring with an additional key/value pair variables for destructuring.

var object = { item: { a: 'a0', b: 'b0' } },
    key = 'b',
    value;

({ [key]: value } = object.item);

console.log(value);