Underscore.js - 没有和差异方法麻烦 [英] Underscore.js - without and difference methods trouble

问题描述

我正在尝试使用 underscore.js 库中的 _.without 和 _.difference 方法，但没有成功.

I am trying to use the _.without and _.difference methods in the underscore.js library with no luck.

这是一些代码.

var someIds = _.pluck(parsedID1, 'id');
var otherIds = _.pluck(parsedID2, 'id);

这里是麻烦开始的地方，我想从 someId 的列表中删除所有 otherId.所以我根据网站有两个选择，要么我可以使用 _.difference ||_.没有.我像这样使用它们...

Here is where the trouble starts, I want to remove all of the otherIds out of the someId's list. So I have two options according to the website, either I can use _.difference || _.without. I use them like so...

var newArray = _.without(_.toArray(someIds), _.toArray(otherIds));

我也尝试使用 _.difference 来执行此操作，但除了将第一个参数的副本返回到函数中之外，我似乎无法获得其他方法.我也试过将参数传递给函数而不使用 _.toArray() 但同样的事情发生了.以前有没有人遇到过这个错误?

I have also tried to do this with _.difference as well, but I cant seem to get the methods to do anything other than return a copy of the first argument into the function. I have also tried passing the arguments into the functions without using the _.toArray() but the same thing happens.Has anyone ever encountered this error before?

我已经尝试了下面建议的方法.我会给出更多的代码，希望能解决这个问题.

I have tried the way as proposed below. I will give some more code in hopes of fixing this.

我作为参数传入的数组采用以下格式.

The arrays that I am passing in as arguments are in the following format.

var array = ['100004191488120', '100004191488321'];

当我传入 _.difference 时，我执行以下操作:

When I pass into the _.difference I do as follows:

var newArray = _.difference(someIds, otherIds);

如果 someIds 长度为 657 而 otherIds 为 57 我应该得到 600 Id 的结果.相反，无论第一个参数的长度是多少，我都会得到一个结果，即 657.

If someIds length is 657 and otherIds is 57 I should be getting a result of 600 Id's. Instead I get a result of whatever the length of the first argument is, being 657.

编辑 2:已解决

我想出了问题所在，在经历了这么多挫折之后，问题在于我传入的第二个差异论点.

I figured out what the problem was, after all that frustration the problem lied with the second argument to difference I was passing in.

我正在做一个数据库查询并返回一个如下所示的列表.

I was doing a db query and getting back a list that looked like the following.

[{ _id: 514721152222111116666777, facebook: { id: '123456789' } },
 { _id: 514721152222111116666778, facebook: { id: '12345678' } },]

在我收到这些结果后，我想获得 facebook id，所以我做了以下操作，

After I received those results I wanted to get the facebook id so I did the following,

var array = _.pluck(users, 'facebook.id');

这就是问题所在，那个 pluck 给我发回了一个未定义的列表.相反，我之前不得不做 2 次弹拨，而不是一次，如下所示.

Thats were the problem was, that pluck was sending me back a list of undefined. Instead I had to do 2 plucks before instead of one, like the following.

var temp = _.pluck(users, 'facebook'); 
var arrayId = _.pluck(temp, 'id');

感谢@ZenMaster 放弃了关于 _.without && 之间区别的知识._.区别.你的回答是正确的，在一个活页夹之后脑子已经死了，没有看到明显的东西.

Thanks @ZenMaster for dropping the knowledge on the difference between _.without && _.difference. Your answer was correct, was pretty brain-dead after a binder and didn't see the obvious.

推荐答案

1. without 函数的第一个参数不需要 _.toArray
2. without 的第二个(以及更多)参数不是数组 - 它是值的列表".

1. You don't need an _.toArray on the first argument of the without function
2. The second (and more) arguments to the without is not an array - it's a "list" of values.

正确的调用应该是:

var newArray = _.without(['1', '2', '3'], '1', '3');

这将导致:

['2']

在您的情况下，您必须使用 _.difference，如 JSFiddle 在这里.

In your case, you'd have to use _.difference as can be seen on JSFiddle here.

代码如下:

var parsedID1 = [{id: '1', name: 'name1'}, {id: '2', name: 'name2'}];
var parsedID2 = [{id: '1', name: 'name1'}, {id: '3', name: 'name3'}];

var someIds = _.pluck(parsedID1, 'id');
var otherIds = _.pluck(parsedID2, 'id');

console.log(someIds, otherIds);

var newArray = _.difference(someIds, otherIds);

console.log(newArray);

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