有效地将字段从一个数组合并到另外两个数组中

Let's say you've got three arrays of objects:

假设你有三个对象数组:

let a1 = [
  { id: 1, name: 'foo' },
  { id: 2, name: 'bar' },
  { id: 3, name: 'baz' }
]

let a2 = [
  { name: 'foo' },
  { name: 'bar' }
]

let a3 = [
  { name: 'bar' },
  { name: 'baz' }
]

The goal is to use a1 as a source, and add an id field to the elements of a2 and a3 with corresponding name fields in a1. What is an efficient way of accomplishing this? (Note: 'efficient' here meaning 'something more elegant than loops-within-loops-within-loops'.)

目标是使用a1作为源,并在a1和a3的元素中添加id字段,并在a1中添加相应的名称字段。什么是实现这一目标的有效方法? (注意:'高效'在这里意味着'比循环内循环更优雅'。)

The result should look like this:

结果应如下所示:

a2: [
  { id: 1, name: 'foo' },
  { id: 2, name: 'bar' }
]

a3: [
  { id: 2, name: 'bar' },
  { id: 3, name: 'baz' }
]

5 个解决方案

#1

You could use a Map for referencing the id of a given name. Then assign.

您可以使用Map来引用给定名称的ID。然后分配。

var a1 = [{ id: 1, name: 'foo' }, { id: 2, name: 'bar' }, { id: 3, name: 'baz' }], 
    a2 = [{ name: 'foo' }, { name: 'bar' }],
    a3 = [{ name: 'bar' }, { name: 'baz' }],
    map = new Map(a1.map(o => [o.name, o.id]));
    
[a2, a3].forEach(a => a.forEach(o => o.id = map.get(o.name)));

console.log(a2);
console.log(a3);

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#2

For an alternative answer, it could be like this.

对于另一种答案,它可能是这样的。

It doesn't include loops and may be the shortest code in the answers.

它不包括循环,可能是答案中最短的代码。

const a1 = [{ id: 1, name: 'foo' }, { id: 2, name: 'bar' }, { id: 3, name: 'baz' }];
const a2 = [{ name: 'foo' }, { name: 'bar' }];
const a3 = [{ name: 'bar' }, { name: 'baz' }];

let f = x => a1.filter(a => x.some(y => y.name === a.name));

console.log(f(a2));
console.log(f(a3));

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#3

a2.forEach((a2Elem) => a2Elem.id = a1.filter((a1Elem) => a1Elem.name === a2Elem.name)[0].id)

#4

I'd first take the indexes of the given names, then just map the array to be merged into:

我首先获取给定名称的索引,然后将要合并的数组映射到:

function combine(mergeInto, base) {
    let indexes = base.map(e => e.name);
    return mergeInto.map(e => ({
        name: e.name,
        id: base[indexes.indexOf(e.name)].id
    }));
}

let a1 = [
    { id: 1, name: 'foo' },
    { id: 2, name: 'bar' },
    { id: 3, name: 'baz' }
]

let a2 = [
    { name: 'foo' },
    { name: 'bar' }
]

let a3 = [
    { name: 'bar' },
    { name: 'baz' }
]

function combine(mergeInto, base) {
    let indexes = base.map(e => e.name);
    return mergeInto.map(e => ({
        name: e.name,
        id: base[indexes.indexOf(e.name)].id
    }));
}

console.log(combine(a3, a1));

#5

A single loop proposal - create a hash table and then merge fields into the arrays - demo below:

单循环提议 - 创建哈希表,然后将字段合并到数组中 - 演示如下:

let a1=[{id:1,name:'foo'},{id:2,name:'bar'},{id:3,name:'baz'}], a2=[{name:'foo'},{name:'bar'}], a3=[{name:'bar'},{name:'baz'}];

// create a hash table
let hash = a1.reduce(function(p,c){
  p[c.name] = c;
  return p;
},Object.create(null))

// merge the results
function merge(arr) {
  Object.keys(arr).map(function(e){
    arr[e]['id'] = hash[arr[e].name]['id'];
  });
  return arr;
}

console.log(merge(a2), merge(a3));

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#1