TypeScript vs. C#: LINQ
TypeScript 没有等效于 LINQ 的语言集成自然查询方面?不能在 TypeScript 中写入以下 LINQ 语句
var adultUserNames = from u in users where u.Age >= 18 select u.Name;
但是,位于 LINQ 核心的 iE6<T>扩展方法在 TypeScript 中具有等效项(或可以模拟)。
Aggregate All Any Append Average Cast Concat Contains Count DefaultIfEmpty Distinct ElementAt ElementAtOrDefault Empty Except First FirstOrDefault List.ForEach GroupBy Intersect Last LastOrDefault Max Min OfType OrderBy / ThenBy Reverse Select SelectMany Single SingleOrDefault Skip SkipWhile Sum Take TakeWhile Union Where Zip
Aggregate
// C# var leftToRight = users.Aggregate(initialValue, (a, u) => /* ... */); // TypeScript const leftToRight = users.reduce((a, u) => /* ... */, initialValue); const rightToLeft = users.reduceRight((a, u) => /* ... */, initialValue);
All
// C# var allReady = users.All(u => u.IsReady); // TypeScrip tconst allReady = users.every(u => u.isReady);
Any
// C# var isDirty = users.Any(u => u.IsDirty); // TypeScript const isDirty = users.some(u => u.isDirty);
Append
// C# var allUsers = users.Append(oneMoreUser); // TypeScript const allUsers = [ ...users, oneMoreUser ];
Average
// C# var avgAge = users.Average(u => u.Age); // TypeScript if (users.length < 1) { throw new Error(‘source contains no elements‘); } const avgAge = users.reduce((a, u) => a + u.age, 0) / users.length;
Cast
// C# var people = users.Cast<Person>(); // TypeScript const people = users as Person[]; // Note: not semantically the same. The C# version throws an exception // if any of the users can‘t be cast to type Person. //注意:在语义上不同。C# 版本引发异常如果无法强制转换为键入 Person 的任何用户。
Concat
// C# var allUsers = users.Concat(moreUsers); // TypeScript const allUsers = [ ...users, ...moreUsers ];
Contains
// C# var hasAdmin = users.Contains(admin); // TypeScript const hasAdmin = users.includes(admin); // Use a polyfill for IE support
Count
// C# var n = users.Count(); // TypeScript const n = users.length;
DefaultIfEmpty
// C# var nonEmptyUsers = Enumerable.DefaultIfEmpty(users); // TypeScript const nonEmptyUsers = users.length ? users : [ null ];
Distinct
// C# var uniqueNames = users.Select(u => u.Name).Distinct(); // TypeScript const uniqueNames = Object.keys(users.map(u => u.name).reduce((un, u) => ({ ...un, n }),{}));
ElementAt
// C# var nth = users.ElementAt(n); // TypeScript if (n < 0 || n > users.length) { throw new Error(‘Index was out of range‘); } const nth = users[n];
ElementAtOrDefault
// C# var nth = users.ElementAtOrDefault(n); // TypeScript const nth = users[n];
Empty
// C# var noUsers = IEnumerable.Empty<User>();//?.NET 4.0 没找到 找到的是DefaultIfEmpty // var noUsers = IEnumerable.DefaultIfEmpty<User>(); // TypeScript const noUsers: User[] = []; const noUsers = [] as User[];
Except
// C# var maleUsers = users.Except(femaleUsers); // TypeScript const maleUsers = users.filter ( u => !femaleUsers.includes(u) // Use a polyfill for IE support(Use a polyfill for IE support) );
First
// C# var first = users.First(); // TypeScript if (users.length < 1) { throw new Error(‘Sequence contains no elements‘); } const first = users[0];
FirstOrDefault
// C# var first = users.FirstOrDefault(); // TypeScript const first = users[0];
List.ForEach
// C# users.ToList().ForEach(u => /* ... */); // TypeScript users.forEach(u => /* ... */);
GroupBy
// C# var usersByCountry = users.GroupBy(u => u.Country); // TypeScript const usersByCountry = users.reduce((ubc, u) => ({ ...ubc, [u.country]: [ ...(ubc[u.country] || []), u ],}), {});
Intersect
// C# var targetUsers = usersWhoClicked.Intersect(usersBetween25And45); // TypeScript const targetUsers = usersWhoClicked.filter(u => usersBetween25And45.includes(u) // Use a polyfill for IE support);
Last
// C# var last = users.Last(); // TypeScrip tif (users.length < 1) { throw new Error(‘Sequence contains no elements‘); } const last = users[users.length - 1];
LastOrDefault
// C# var last = users.LastOrDefault(); // TypeScript const last = users[users.length - 1];
Max
// C# var oldestAge = users.Max(u => u.Age); // TypeScrip tif (users.length < 1) { throw new Error(‘source contains no elements‘); } const oldestAge = users.reduce((oa, u) => Math.max(oa, u.age), 0);
Min
// C# var youngestAge = users.Min(u => u.Age); // TypeScript if (users.length < 1) { t hrow new Error(‘source contains no elements‘); } const youngestAge = users.reduce((ya, u) => Math.min(ya, u.age), Number.MAX_VALUE);
OfType
// C# var bots = users.OfType<Bot>();//根据类型刷新元素 // TypeScript // No equivalent 无等效项
OrderBy / ThenBy
// C# var sorted = users.OrderBy(u => u.Age).ThenBy(u => u.Name); // TypeScript const sorted = users.sort((a, b) => { const ageDiff = b.age - a.age; if (ageDiff) return ageDiff; return a.name.localeCompare(b.name); // Use a polyfill for IE support } );
Reverse
// C# var backwards = users.Reverse(); // TypeScript const backwards = users.reverse();// Caution: users is also reversed! 原数组也翻转了
Select
// C# var names = users.Select(u => u.Name); // TypeScript const names = users.map(u => u.name);
SelectMany
// C# var phoneNumbers = users.SelectMany(u => u.PhoneNumbers); // TypeScript const phoneNumbers = users.reduce((pn, u) => [ ...pn, ...u.phoneNumbers ], []);
Single
// C# var user = users.Single(); // TypeScript if (users.length > 1) { throw new Error(‘The input sequence contains more than one element‘); }else if (!users.length) { throw new Error(‘The input sequence is empty‘); } const user = users[0];
SingleOrDefault
// C# var user = users.Single(); // TypeScript const user = users[0];
Skip
// C# var otherUsers = users.Skip(n); // TypeScript const otherUsers = users.filter((u, i) => i >= n);
SkipWhile
// C# var otherUsers = users.SkipWhile(predicate); // TypeScript let i = 0; while (i < users.length && predicate(users[i++])); const otherUsers = users.slice(i - 1);
Sum
// C# var totalYears = users.Sum(u => u.Age); // TypeScript if (users.length < 1) { throw new Error(‘source contains no elements‘); } const totalYears = users.reduce((ty, u) => ty + u, 0);
Take
// C# var otherUsers = users.Take(n); // TypeScript const otherUsers = users.filter((u, i) => i < n);
TakeWhile
// C# var otherUsers = users.TakeWhile(predicate); // TypeScript let i = 0; while (i < users.length && predicate(users[i++])); const otherUsers = users.slice(0, i - 1);
Union
// C# var allUsers = someUser.Union(otherUsers); // TypeScript const allUsers = otherUsers.reduce((au, u) => au.includes(u) ? au : [ ...au, u ]}), someUsers));// Use a polyfill for IE support
Where
// C# var adults = users.Where(u => u.Age >= 18); // TypeScript const adults = users.filter(u => u.age >= 18);
Zip
// C# var matches = buyers.Zip(sellers, (b, s) => new { Buyer = b, Seller = s }); // TypeScript const matches = [] ;for (let i = 0; i < buyers.length && i < sellers.length; i++) { matches.push({ buyer: buyers[i], seller: sellers[i], }); }
水平有限,请大家见谅,翻译的有误,请指出。谢谢
原文地址 https://decembersoft.com/posts/typescript-vs-csharp-linq/