您可以 map :

permittedValues = array.map(function(value) {
  return value.key;
});

在ES6/ES2015中，箭头功能:

In ES6/ES2015 it's even prettier with arrow functions:

permittedValues = array.map(value => value.key);

它可能更漂亮，但是它可能不比for()循环快.

It might be prettier, but it's probably not faster than a for() loop.