ecmascript-6 - es6 中解构获取数组的最后一个元素

Question

在coffeescript中这很简单:

coffee> a = ['a', 'b', 'program']
[ 'a', 'b', 'program' ]
coffee> [_..., b] = a
[ 'a', 'b', 'program' ]
coffee> b
'program'

es6 允许类似的东西吗？

> const [, b] = [1, 2, 3]                              
'use strict'                                           
> b  // it got the second element, not the last one!                      
2                                                      
> const [...butLast, last] = [1, 2, 3]          
SyntaxError: repl: Unexpected token (1:17)                                                                                                                                                        
> 1 | const [...butLast, last] = [1, 2, 3]                                                                                                                                                        
    |                  ^                                                                                                                                                                          
    at Parser.pp.raise (C:\Users\user\AppData\Roaming\npm\node_modules\babel\node_modules\babel-core\node_modules\babylon\lib\parser\location.js:24:13)                                           

当然我可以用 es5 的方式来做 -

const a = b[b.length - 1]

但也许这有点容易因一个错误而消失。啪啪声只能是解构中的最后一件事吗？

Answer 1

console.log('last', [1, 3, 4, 5].slice(-1));
console.log('second_to_last', [1, 3, 4, 5].slice(-2));