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
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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）。
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AggregateAllAnyAppendAverageCastConcatContainsCountDefaultIfEmptyDistinctElementAtElementAtOrDefaultEmptyExceptFirstFirstOrDefaultList.ForEachGroupByIntersectLastLastOrDefaultMaxMinOfTypeOrderBy / ThenByReverseSelectSelectManySingleSingleOrDefaultSkipSkipWhileSumTakeTakeWhileUnionWhereZip |
Aggregate
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// C#var leftToRight = users.Aggregate(initialValue, (a, u) => /* ... */); // TypeScriptconst leftToRight = users.reduce((a, u) => /* ... */, initialValue);const rightToLeft = users.reduceRight((a, u) => /* ... */, initialValue); |
All
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// C#var allReady = users.All(u => u.IsReady); // TypeScriptconst allReady = users.every(u => u.isReady); |
Any
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// C#var isDirty = users.Any(u => u.IsDirty); // TypeScriptconst isDirty = users.some(u => u.isDirty); |
Append
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// C#var allUsers = users.Append(oneMoreUser); // TypeScriptconst allUsers = [ ...users, oneMoreUser ]; |
Average
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// C#var avgAge = users.Average(u => u.Age); // TypeScriptif (users.length < 1) { throw new Error('source contains no elements');}const avgAge = users.reduce((a, u) => a + u.age, 0) / users.length; |
Cast
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// C#var people = users.Cast<Person>(); // TypeScriptconst 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
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// C#var allUsers = users.Concat(moreUsers); // TypeScriptconst allUsers = [ ...users, ...moreUsers ]; |
Contains
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// C#var hasAdmin = users.Contains(admin); // TypeScriptconst hasAdmin = users.includes(admin); // Use a polyfill for IE support |
Count
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// C#var n = users.Count(); // TypeScriptconst n = users.length; |
DefaultIfEmpty
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// C#var nonEmptyUsers = Enumerable.DefaultIfEmpty(users); // TypeScriptconst nonEmptyUsers = users.length ? users : [ null ]; |
Distinct
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// C#var uniqueNames = users.Select(u => u.Name).Distinct(); // TypeScriptconst uniqueNames = Object.keys(users.map(u => u.name).reduce((un, u) => ({ ...un, n }),{})); |
ElementAt
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// C#var nth = users.ElementAt(n); // TypeScriptif (n < 0 || n > users.length) { throw new Error('Index was out of range');}const nth = users[n]; |
ElementAtOrDefault
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// C#var nth = users.ElementAtOrDefault(n); // TypeScriptconst nth = users[n]; |
Empty
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// C#var noUsers = IEnumerable.Empty<User>();//?.NET 4.0 没找到 找到的是DefaultIfEmpty//var noUsers = IEnumerable.DefaultIfEmpty<User>(); // TypeScriptconst noUsers: User[] = [];const noUsers = [] as User[]; |
Except
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// C#var maleUsers = users.Except(femaleUsers); // TypeScriptconst maleUsers = users.filter(u => !femaleUsers.includes(u) // Use a polyfill for IE support（Use a polyfill for IE support）); |
First
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// C#var first = users.First(); // TypeScriptif (users.length < 1) { throw new Error('Sequence contains no elements');}const first = users[0]; |
FirstOrDefault
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// C#var first = users.FirstOrDefault(); // TypeScriptconst first = users[0]; |
List.ForEach
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// C#users.ToList().ForEach(u => /* ... */); // TypeScriptusers.forEach(u => /* ... */); |
GroupBy
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// C#var usersByCountry = users.GroupBy(u => u.Country); // TypeScriptconst usersByCountry = users.reduce((ubc, u) =>({ ...ubc, [u.country]: [ ...(ubc[u.country] || []), u ],}),{}); |
Intersect
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// C#var targetUsers = usersWhoClicked.Intersect(usersBetween25And45); // TypeScriptconst targetUsers = usersWhoClicked.filter(u => usersBetween25And45.includes(u) // Use a polyfill for IE support); |
Last
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// C#var last = users.Last(); // TypeScriptif (users.length < 1) { throw new Error('Sequence contains no elements');}const last = users[users.length - 1]; |
LastOrDefault
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// C#var last = users.LastOrDefault(); // TypeScriptconst last = users[users.length - 1]; |
Max
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// C#var oldestAge = users.Max(u => u.Age); // TypeScriptif (users.length < 1) { throw new Error('source contains no elements');}const oldestAge = users.reduce((oa, u) => Math.max(oa, u.age), 0); |
Min
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// C#var youngestAge = users.Min(u => u.Age); // TypeScriptif (users.length < 1) { throw new Error('source contains no elements');}const youngestAge = users.reduce((ya, u) => Math.min(ya, u.age), Number.MAX_VALUE); |
OfType
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// C#var bots = users.OfType<Bot>();//根据类型刷新元素 // TypeScript// No equivalent 无等效项 |
OrderBy / ThenBy
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// C#var sorted = users.OrderBy(u => u.Age).ThenBy(u => u.Name); // TypeScriptconst 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
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// C#var backwards = users.Reverse(); // TypeScriptconst backwards = users.reverse();// Caution: users is also reversed! 原数组也翻转了 |
Select
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// C#var names = users.Select(u => u.Name); // TypeScriptconst names = users.map(u => u.name); |
SelectMany
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// C#var phoneNumbers = users.SelectMany(u => u.PhoneNumbers); // TypeScriptconst phoneNumbers = users.reduce((pn, u) => [ ...pn, ...u.phoneNumbers ], []); |
Single
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// C#var user = users.Single(); // TypeScriptif (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
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// C#var user = users.Single(); // TypeScriptconst user = users[0]; |
Skip
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// C#var otherUsers = users.Skip(n); // TypeScriptconst otherUsers = users.filter((u, i) => i >= n); |
SkipWhile
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// C#var otherUsers = users.SkipWhile(predicate); // TypeScriptlet i = 0;while (i < users.length && predicate(users[i++])); const otherUsers = users.slice(i - 1); |
Sum
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// C#var totalYears = users.Sum(u => u.Age); // TypeScriptif (users.length < 1) { throw new Error('source contains no elements');}const totalYears = users.reduce((ty, u) => ty + u, 0); |
Take
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// C#var otherUsers = users.Take(n); // TypeScriptconst otherUsers = users.filter((u, i) => i < n); |
TakeWhile
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// C#var otherUsers = users.TakeWhile(predicate); // TypeScriptlet i = 0;while (i < users.length && predicate(users[i++])); const otherUsers = users.slice(0, i - 1); |
Union
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// C#var allUsers = someUser.Union(otherUsers); // TypeScriptconst allUsers = otherUsers.reduce((au, u) => au.includes(u) ? au : [ ...au, u ]}), someUsers));// Use a polyfill for IE support |
Where
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// C#var adults = users.Where(u => u.Age >= 18); // TypeScriptconst adults = users.filter(u => u.age >= 18); |
Zip
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// C#var matches = buyers.Zip(sellers, (b, s) => new { Buyer = b, Seller = s }); // TypeScriptconst 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/