[英]Backbone.js: compare model attributes in a collection
I have a collection of unlimited scope (can be 0, can be 1000, can be a million). 我有一个无限范围的集合(可以是0,可以是1000,可以是一百万)。 I need to search the attributes of every model in the collection and return the attributes (and their values) that are the same.
我需要搜索集合中每个模型的属性,并返回相同的属性(及其值)。
For example, if I have the following three models in the collection: 例如,如果我在集合中有以下三个模型:
modelOne:
color: "red"
age: 10
size: "large"
modelTwo:
color: "red"
age: 11
size: "medium"
modelThree:
color: "red"
age: 9
size: "large"
I need the app to return color: "red"
(or some other derivation that can be parsed), since it is the only attribute that is equal across all three models. 我需要应用程序返回
color: "red"
(或其他一些可以解析的派生),因为它是所有三个模型中唯一相同的属性。
Edit John Munsch's solution worked very well, but now the requirements have changed in that some attributes can now be arrays. 编辑 John Munsch的解决方案非常有效,但现在需求已经改变,因为某些属性现在可以是数组。 Is there a way to compare regular attributes, and attributes that are arrays?
有没有办法比较常规属性和数组属性?
New code example: 新代码示例:
modelOne:
color: "red"
age: 10
sizes: ["small", "large"]
modelTwo:
color: "red"
age: 9
sizes: ["small", "large"]
Here's a quick jsFiddle with my version of an answer : http://jsfiddle.net/JohnMunsch/3NMGD/ 这是一个快速的jsFiddle与我的答案版本: http : //jsfiddle.net/JohnMunsch/3NMGD/
Note: Both the jsFiddle and the code below have been updated to reflect the changed requirements of the question. 注意:jsFiddle和下面的代码都已更新,以反映问题的更改要求。
var model = [
{
color: "red",
age: 10,
size: [ "small", "large" ]
},
{
color: "red",
age: 11,
size: [ "small", "large" ]
},
{
color: "red",
age: 9,
size: [ "small", "large" ]
}
];
function findCommonalities(data) {
if (data.length > 0) {
// It's safe enough to get the list of keys from the very first
// element. If the later ones differ, you know that the keys they
// had but the first element didn't are guaranteed not to be in
// the common set anyway because the first element didn't
// have them.
var keys = _.keys(data[0]);
var commonalities = { };
_.each(keys,
function (key) {
var values = _.pluck(data, key);
if (values.length == data.length) {
// Sadly calling _.uniq() won't work when the values
// plucked out are arrays themselves. It calls ===
// and that's not sufficient for arrays.
if (_.isArray(values[0])) {
// However, we can get a little tricky here.
// What if we _.zip() together all of the arrays
// (assuming the ordering for each array is the
// same) then we'll end up with an array of
// arrays where each one can again be tested
// with _.uniq() because each one will contain
// the same value taken from each array.
var zippedValues = _.zip(values);
console.log("zippedValues", zippedValues);
if (!_.find(zippedValues,
function (zippedValue) {
var uniqueValues = _.uniq(zippedValue);
// Note: This test is the inverse of the
// one below. We're trying to find any
// array that has more than one value in
// it. If we do then there's some
// variance.
return uniqueValues.length != 1;
})) {
// We didn't find any arrays that had any
// variance so we want this as well.
commonalities[key] = values[0];
}
} else {
var uniqueValues = _.uniq(values);
if (uniqueValues.length == 1) {
commonalities[key] = uniqueValues[0];
}
}
}
}
);
return commonalities;
} else {
return { };
}
}
console.log("commonalities: ", findCommonalities(model));
Performance seems fine with a small number of keys and a small number of items, but you'd need to test it with a million records and a large number of keys. 少量按键和少量项目的性能似乎很好,但您需要使用一百万条记录和大量按键进行测试。
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