javascript 使用 lo-dash/underscore 从 _.pluck 获取对象
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Getting an object from _.pluck with lo-dash/underscore
提问by JJJollyjim
I have an object structured like this:
我有一个这样结构的对象：
var my_object = {
first_item: {important_number: 4},
second_item: {important_number: 6},
}
However, I would like an object structured like this:
但是，我想要一个结构如下的对象：
{
first_item: 4,
second_item: 6,
}
I would have expected to be able to get this result with _.pluck:
我本来希望能够得到这个结果_.pluck：
_.pluck(my_object, "important_number")
But this gives me:
但这给了我：
[0: 4, 1: 6]
Good, but I need the actual names of the objects. I fiddled around and ended up with this:
很好，但我需要对象的实际名称。我摆弄了一下，最后得到了这个：
_.reduce(my_object, function(memo, val, key) {
memo[key] = val.content;
return memo;
}, {});
Which has the desired effect, but isn't as simple as I would?like. Is there a better solution in underscore/lodash, or is this the best it will get?
哪个具有预期的效果，但并不像我想要的那么简单？下划线/lodash 是否有更好的解决方案，或者这是最好的解决方案？
回答by John-David Dalton
In Lo-Dash you could also use _.transform, a more powerful alternative to _.reduce:
在 Lo-Dash 中，您还可以使用_.transform，这是_.reduce的更强大的替代品：
_.transform(my_object, function(memo, val, key) {
memo[key] = val.important_number;
});
回答by TWiStErRob
Actually what you're describing - that is "pluckfor object values" - can be written as:
实际上你所描述的 - 即“pluck对象值” - 可以写成：
_.mapValues(my_object, "important_number")
See documentation of _.mapValues.
请参阅 的文档_.mapValues。
_.createCallback- which does the string to property magic - is used all over the place in Lo-Dash: search for "_.pluck" style callback.
_.createCallback- 将字符串转换为属性魔法 - 在 Lo-Dash 中到处使用：搜索"_.pluck" style callback.
回答by Gilad Peleg
I know it's fun to use Lo-Dash/Underscore, but if you have to use 2 functions instead of just using a regular loop, you're better off using 'old_school' coding style:
我知道使用 Lo-Dash/Underscore 很有趣，但是如果您必须使用 2 个函数而不是仅使用常规循环，则最好使用“old_school”编码风格：
var data = {
first_item: {important_number: 4},
second_item: {important_number: 6},
};
var obj = {};
for (var i in data) {
if (data.hasOwnProperty(i)) obj[i] = data[i].important_number;
}
Just to prove my point, I updated your JsPerf to include the regular for loop, and watch the magic: http://jsperf.com/getting-an-object-from-pluck/2
为了证明我的观点，我更新了您的 JsPerf 以包含常规 for 循环，并观看魔术：http: //jsperf.com/getting-an-object-from-pluck/2
Regular For Loopis at least 2xfaster than any other method you guys posted here. And that's mainly because it only traverses the object once.
常规 For 循环至少比你们在此处发布的任何其他方法快2倍。这主要是因为它只遍历对象一次。
