假设我有以下内容:
var array =
[
{"name":"Joe", "age":17},
{"name":"Bob", "age":17},
{"name":"Carl", "age": 35}
]
获得所有不同年龄的数组的最佳方法是什么，这样我就得到了一个结果数组:
[17, 35]
是否有一些方法，我可以选择结构数据或更好的方法，这样我就不必遍历每个数组检查“年龄”的值，并检查另一个数组是否存在，如果没有添加它?
如果有某种方法可以让我不用迭代就能得到不同的年龄……
目前效率低下的方式，我想改进…如果它的意思不是“数组”是一个对象的数组，而是一个对象的“映射”与一些唯一的键(即。"1,2,3")也可以。我只是在寻找最高效的方式。
以下是我目前的做法，但对我来说，迭代似乎只是为了提高效率，即使它确实有效……
var distinct = []
for (var i = 0; i < array.length; i++)
if (array[i].age not in distinct)
distinct.push(array[i].age)
清洁解决方案
export abstract class Serializable<T> {
equalTo(t: Serializable<T>): boolean {
return this.hashCode() === t.hashCode();
}
hashCode(): string {
throw new Error('Not Implemented');
}
}
export interface UserFields {
firstName: string;
lastName: string;
}
export class User extends Serializable<User> {
constructor(private readonly fields: UserFields) {
super();
}
override hashCode(): string {
return `${this.fields.firstName},${this.fields.lastName}`;
}
}
const list: User[] = [
new User({ firstName: 'first', lastName: 'user' }),
new User({ firstName: 'first', lastName: 'user' }),
new User({ firstName: 'second', lastName: 'user' }),
new User({ firstName: 'second', lastName: 'user' }),
new User({ firstName: 'third', lastName: 'user' }),
new User({ firstName: 'third', lastName: 'user' }),
];
/**
* Let's create an map
*/
const userHashMap = new Map<string, User>();
/**
* We are adding each user into the map using user's hashCode value
*/
list.forEach((user) => userHashMap.set(user.hashCode(), user));
/**
* Then getting the list of users from the map,
*/
const uniqueUsers = [...userHashMap.values()];
/**
* Let's print and see we did right?
*/
console.log(uniqueUsers.map((e) => e.hashCode()));
@Travis J字典答案在Typescript类型安全函数的方法
const uniqueBy = <T, K extends keyof any>(
list: T[] = [],
getKey: (item: T) => K,
) => {
return list.reduce((previous, currentItem) => {
const keyValue = getKey(currentItem)
const { uniqueMap, result } = previous
const alreadyHas = uniqueMap[keyValue]
if (alreadyHas) return previous
return {
result: [...result, currentItem],
uniqueMap: { ...uniqueMap, [keyValue]: true }
}
}, { uniqueMap: {} as Record<K, any>, result: [] as T[] }).result
}
const array = [{ "name": "Joe", "age": 17 }, { "name": "Bob", "age": 17 }, { "name": "Carl", "age": 35 }];
console.log(uniqueBy(array, el => el.age))
// [
// {
// "name": "Joe",
// "age": 17
// },
// {
// "name": "Carl",
// "age": 35
// }
// ]
现在我们可以在相同的键和相同的值的基础上唯一对象
const arr = [{"name":"Joe", "age":17},{"name":"Bob", "age":17}, {"name":"Carl", "age": 35},{"name":"Joe", "age":17}]
let unique = []
for (let char of arr) {
let check = unique.find(e=> JSON.stringify(e) == JSON.stringify(char))
if(!check) {
unique.push(char)
}
}
console.log(unique)
/ / / /输出:::[{名称:“乔”,年龄:17},{名称:“Bob”,年龄:17},{名称:“卡尔”,年龄:35}]
