javascript-lodash-基于多个属性创建唯一列表 [英] javascript - lodash - create a unique list based on multiple attributes

问题描述

我的收藏看起来像这样.

My collection looks like this.

  var list = [{id:'12345', sequence:null}, {id:'12346', sequence:null}, {id:'12347', sequence:null}, {id:'12348', sequence:1}, {id:'12348', sequence:2}, {id:'12349', sequence:1}, {id:'12349', sequence:1}];

我正在尝试获取唯一列表，以便具有相同ID和序列的对象仅返回其中一个对象(这里有2个{{id:'12349'，sequence:1})

I am trying to get a unique list so that object with same id AND sequence will only return one of the objects (we have 2 here- {id:'12349', sequence:1})

我的代码

  var uniqueList = _.uniq(list, function(obj) {
    return obj.id && obj.sequence;
  });

我们可以像这样使用lodash uniq吗?解决此问题的方法是什么?

can we use lodash uniq like this? what is the approach to fix this issue?

推荐答案

您可以使用 uniqBy()计算生成列表的标准，其中iteratee回调返回集合中每个项目的id和sequence的合并值.当您只希望具有特定属性作为唯一性标准时，以下解决方案非常有用，尤其是当集合中的每个对象可能不仅具有id和sequence属性时.

You can use uniqBy() to compute the criterion by which the list is generated wherein the iteratee callback returns the joined value of id and sequence of each item of the colection. The solution below works great when you only want to have specific properties to be the criterion of uniqueness especially when each object in your collection may not only have the id and sequence properties.

var result = _.uniqBy(list, v => [v.id, v.sequence].join());

var list = [{
  id: '12345',
  sequence: null
}, {
  id: '12346',
  sequence: null
}, {
  id: '12347',
  sequence: null
}, {
  id: '12348',
  sequence: 1
}, {
  id: '12348',
  sequence: 2
}, {
  id: '12349',
  sequence: 1
}, {
  id: '12349',
  sequence: 1
}, {
  id: '123490',
  sequence: 1,
  extra: 1
}, {
  id: '123490',
  sequence: 1,
  extra: 2
}];

var result = _(list)
  .uniqBy(v => [v.id, v.sequence].join())
  .value();

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.12.0/lodash.js"></script>

或者，如果您具有包含非原始值(对象或数组)的属性用作条件，那么您仍然可以使用上面的解决方案，而不必加入值数组，而必须使用 JSON.stringify()

Alternatively, if you have properties that contains non-primitive values (objects or arrays) to be used as the criterion then you can still use the solution above but instead joining the array of values, you have to use JSON.stringify()

var result = _.uniqBy(list, v => JSON.stringify([v.id, v.sequence]));

var list = [{
  id: '12345',
  sequence: null
}, {
  id: '12346',
  sequence: null
}, {
  id: '12347',
  sequence: null
}, {
  id: '12348',
  sequence: 1
}, {
  id: '12348',
  sequence: 2
}, {
  id: '12349',
  sequence: 1
}, {
  id: '12349',
  sequence: 1
}, {
  id: '123490',
  sequence: 1,
  extra: 1
}, {
  id: '123490',
  sequence: 1,
  extra: 2
}];

var result = _.uniqBy(list, v => JSON.stringify([v.id, v.sequence]));

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.12.0/lodash.js"></script>

更新:

对于lodash3解决方案，对于具有原始值的属性，您仍可以在第一个解决方案中使用

For the lodash3 solution, for properties with primitive values, you can still use the pattern in the first solution using uniq().

var result = _.uniq(list, v => [v.id, v.sequence].join());

var list = [{
  id: '12345',
  sequence: null
}, {
  id: '12346',
  sequence: null
}, {
  id: '12347',
  sequence: null
}, {
  id: '12348',
  sequence: 1
}, {
  id: '12348',
  sequence: 2
}, {
  id: '12349',
  sequence: 1
}, {
  id: '12349',
  sequence: 1
}, {
  id: '123490',
  sequence: 1,
  extra: 1
}, {
  id: '123490',
  sequence: 1,
  extra: 2
}];

var result = _.uniq(list, v => [v.id, v.sequence].join());

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.10.1/lodash.js"></script>

对于非原始属性，您仍然可以将上面的第二个示例与

And for the non-primitive properties, you can still use the 2nd example above with uniq()

var result = _.uniq(list, v => JSON.stringify([v.id, v.sequence]));

var list = [{
  id: '12345',
  sequence: null
}, {
  id: '12346',
  sequence: null
}, {
  id: '12347',
  sequence: null
}, {
  id: '12348',
  sequence: 1
}, {
  id: '12348',
  sequence: 2
}, {
  id: '12349',
  sequence: 1
}, {
  id: '12349',
  sequence: 1
}, {
  id: '123490',
  sequence: 1,
  extra: 1
}, {
  id: '123490',
  sequence: 1,
  extra: 2
}];

var result = _.uniq(list, v => JSON.stringify([v.id, v.sequence]));

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.10.1/lodash.js"></script>

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