如何在Javascript中从集合数组中提取键值

var collection = [{key: 'value1'}, {key: 'value2'}, {key: 'value3'}];
var keys = [];

for (var i = 0; i < collection.length; i++) {
  keys.push(collection[i].key);
}

console.log(keys); // 输出 ['value1', 'value2', 'value3']

var collection = [{key: 'value1'}, {key: 'value2'}, {key: 'value3'}];
var keys = collection.map(function(item) {
  return item.key;
});

console.log(keys); // 输出 ['value1', 'value2', 'value3']

var collection = [{key: 'value1'}, {key: 'value2'}, {key: 'value3'}];
var keys = collection.reduce(function(acc, item) {
  acc.push(item.key);
  return acc;
}, []);

console.log(keys); // 输出 ['value1', 'value2', 'value3']

var collection = [{key: 'value1'}, {key: 'value2'}, {key: 'value3'}];
var keys = [];

collection.forEach(function(item) {
  keys.push(item.key);
});

console.log(keys); // 输出 ['value1', 'value2', 'value3']