高效地将字段从一个数组合并到另外两个数组中

Question

假设您有三个对象数组：

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' }
]

目标是使用a1作为源，并在a2和a3的元素中添加一个id字段，并在a1中具有相应的name字段。实现此目的的有效方法是什么？(注意："高效"在这里的意思是"比循环中循环更优雅的东西"。

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' }
]

Answer 1

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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Answer 2

对于替代答案，可能是这样的。

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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Answer 3

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

Answer 4

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));

Answer 5

单个循环建议 - 创建一个hash table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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