javascript - 基于多个属性在数组中查找唯一对象

Question

我需要从数组中找到基于2个属性的唯一对象,如下所示.当"class"和"fare"匹配时,我需要提取唯一值并将它们放入结果数组中.

资源:

var arr = [{class:"second", fare: "a"}, 
 {class:"second", fare: "b"},
 {class:"first", fare: "a"},
 {class:"first", fare: "a"},
 {class:"second", fare: "a"},
 {class:"first", fare: "c"}
]

预期结果:

var result = [{class:"second", fare: "a"},
 {class:"second", fare: "b"},
 {class:"first", fare: "a"},
 {class:"first", fare: "c"}
]

我查看了SO,并且能够找到基于一个属性过滤的答案(按属性创建唯一对象的数组),但找不到哪个可以基于2个属性.

Answer 1

您可以为哈希表构建一个组合键,以过滤给定数组.

var arr = [{ class: "second", fare: "a" }, { class: "second", fare: "b" }, { class: "first", fare: "a" }, { class: "first", fare: "a" }, { class: "second", fare: "a" }, { class: "first", fare: "c" }],
    result = arr.filter(function (a) {
        var key = a.class + '|' + a.fare;
        if (!this[key]) {
            this[key] = true;
            return true;
        }
    }, Object.create(null));

console.log(result);

Answer 2

使用组合键和地图

const array = [
 { class: "second", fare: "a" }, 
 { class: "second", fare: "b" }, 
 { class: "first", fare: "a" }, 
 { class: "first", fare: "a" }, 
 { class: "second", fare: "a" }, 
 { class: "first", fare: "c" }
];

console.log(unique(array, ['class', 'fare']));

function unique(arr, keyProps) {
 const kvArray = arr.map(entry => {
  const key = keyProps.map(k => entry[k]).join('|');
  return [key, entry];
 });
 const map = new Map(kvArray);
 return Array.from(map.values());
}

Answer 3

嘿，你可以使用这个方法

const unique = (arr, props = []) => [...new Map(arr.map(entry => [props.map(k => entry[k]).join('|'), entry])).values()];

const array = [
    {
        class: 'second',
        fare: 'a', 
    },
    {
        class: 'second',
        fare: 'b', 
    },
    {
        class: 'first',
        fare: 'a', 
    },
    {
        class: 'first',
        fare: 'a', 
    },
    {
        class: 'second',
        fare: 'a', 
    },
    {
        class: 'first',
        fare: 'c',
    },
];

const newArr = unique(array, ['class', 'fare']);

console.log(newArr) // [{ class: 'second', fare: 'a' }, { class: 'second', fare: 'b' }, { class: 'first', fare: 'a' }, { class: 'first', fare: 'c' }]