TypeScript vs. C#: LINQ
<p style="text-align: center">TypeScript vs. C#: LINQ</p><p>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</p>
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<pre class="brush:csharp;gutter:true;">var adultUserNames =from u in userswhere u.Age >= 18select u.Name;
</pre>
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<p>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）。</p>
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<pre class="brush:csharp;gutter:true;">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
</pre>
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<h3>Aggregate</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var leftToRight = users.Aggregate(initialValue, (a, u) => /* ... */);
// TypeScript
const leftToRight = users.reduce((a, u) => /* ... */, initialValue);
const rightToLeft = users.reduceRight((a, u) => /* ... */, initialValue);
</pre>
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<h3>All</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var allReady = users.All(u => u.IsReady);
// TypeScrip
tconst allReady = users.every(u => u.isReady);
</pre>
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<h3>Any</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var isDirty = users.Any(u => u.IsDirty);
// TypeScript
const isDirty = users.some(u => u.isDirty);
</pre>
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<h3>Append</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var allUsers = users.Append(oneMoreUser);
// TypeScript
const allUsers = [ ...users, oneMoreUser ];</pre>
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<h3>Average</h3>
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<pre class="brush:csharp;gutter:true;">// 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;</pre>
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<h3>Cast</h3>
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<pre class="brush:csharp;gutter:true;">// 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。 </pre>
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<h3>Concat</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var allUsers = users.Concat(moreUsers);
// TypeScript
const allUsers = [ ...users, ...moreUsers ];</pre>
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<h3>Contains</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var hasAdmin = users.Contains(admin);
// TypeScript
const hasAdmin = users.includes(admin); // Use a polyfill for IE support</pre>
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<h3>Count</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var n = users.Count();
// TypeScript
const n = users.length;</pre>
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<h3>DefaultIfEmpty</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var nonEmptyUsers = Enumerable.DefaultIfEmpty(users);
// TypeScript
const nonEmptyUsers = users.length ? users : [ null ]; </pre>
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<h3>Distinct</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var uniqueNames = users.Select(u => u.Name).Distinct();
// TypeScript
const uniqueNames = Object.keys(users.map(u => u.name).reduce((un, u) => ({ ...un, n }),{}));</pre>
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<h3>ElementAt</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var nth = users.ElementAt(n);
// TypeScript
if (n < 0 || n > users.length) {
throw new Error('Index was out of range');
}
const nth = users; </pre>
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<h3>ElementAtOrDefault</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var nth = users.ElementAtOrDefault(n);
// TypeScript
const nth = users;</pre>
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<h3>Empty</h3>
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<pre class="brush:csharp;gutter:true;">// 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[];</pre>
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<h3>Except</h3>
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<pre class="brush:csharp;gutter:true;">// 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）
); </pre>
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<h3>First</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var first = users.First();
// TypeScript
if (users.length < 1) {
throw new Error('Sequence contains no elements');
}
const first = users;</pre>
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<h3>FirstOrDefault</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var first = users.FirstOrDefault();
// TypeScript
const first = users;</pre>
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<h3>List.ForEach</h3>
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<pre class="brush:csharp;gutter:true;">// C#
users.ToList().ForEach(u => /* ... */);
// TypeScript
users.forEach(u => /* ... */);</pre>
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<h3>GroupBy</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var usersByCountry = users.GroupBy(u => u.Country);
// TypeScript
const usersByCountry = users.reduce((ubc, u) =>
({
...ubc,
: [ ...(ubc || []), u ],}),
{});</pre>
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<h3>Intersect</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var targetUsers = usersWhoClicked.Intersect(usersBetween25And45);
// TypeScript
const targetUsers = usersWhoClicked.filter(u =>usersBetween25And45.includes(u) // Use a polyfill for IE support);</pre>
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<h3>Last</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var last = users.Last();
// TypeScrip
tif (users.length < 1) {
throw new Error('Sequence contains no elements');
}
const last = users;</pre>
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<h3>LastOrDefault</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var last = users.LastOrDefault();
// TypeScript
const last = users;</pre>
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<h3>Max</h3>
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<pre class="brush:csharp;gutter:true;">// 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);</pre>
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<h3>Min</h3>
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<pre class="brush:csharp;gutter:true;">// 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);</pre>
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<h3>OfType</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var bots = users.OfType<Bot>();//根据类型刷新元素
// TypeScript
// No equivalent 无等效项</pre>
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<h3>OrderBy / ThenBy</h3>
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<pre class="brush:csharp;gutter:true;">// 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
}
);</pre>
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<h3>Reverse</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var backwards = users.Reverse();
// TypeScript
const backwards = users.reverse();// Caution: users is also reversed! 原数组也翻转了</pre>
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<h3>Select</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var names = users.Select(u => u.Name);
// TypeScript
const names = users.map(u => u.name); </pre>
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<h3>SelectMany</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var phoneNumbers = users.SelectMany(u => u.PhoneNumbers);
// TypeScript
const phoneNumbers = users.reduce((pn, u) => [ ...pn, ...u.phoneNumbers ], []); </pre>
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<h3>Single</h3>
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<pre class="brush:csharp;gutter:true;">// 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;</pre>
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<h3>SingleOrDefault</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var user = users.Single();
// TypeScript
const user = users; </pre>
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<h3>Skip</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var otherUsers = users.Skip(n);
// TypeScript
const otherUsers = users.filter((u, i) => i >= n); </pre>
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<h3>SkipWhile</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var otherUsers = users.SkipWhile(predicate);
// TypeScript
let i = 0;
while (i < users.length && predicate(users));
const otherUsers = users.slice(i - 1); </pre>
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<h3>Sum</h3>
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<pre class="brush:csharp;gutter:true;">// 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);</pre>
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<h3>Take</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var otherUsers = users.Take(n);
// TypeScript
const otherUsers = users.filter((u, i) => i < n);</pre>
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<h3>TakeWhile</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var otherUsers = users.TakeWhile(predicate);
// TypeScript
let i = 0;
while (i < users.length && predicate(users));
const otherUsers = users.slice(0, i - 1); </pre>
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<h3>Union</h3>
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<pre class="brush:csharp;gutter:true;">// 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</pre>
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<h3>Where</h3>
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<pre class="brush:csharp;gutter:true;">// C#
var adults = users.Where(u => u.Age >= 18);
// TypeScript
const adults = users.filter(u => u.age >= 18); </pre>
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<h3>Zip</h3>
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<pre class="brush:csharp;gutter:true;">// 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, seller: sellers,});
}
</pre>
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<p>水平有限，请大家见谅，翻译的有误，请指出。谢谢</p>
<p>原文地址 https://decembersoft.com/posts/typescript-vs-csharp-linq/</p>
<p> </p>
<p> </p><br><br>
来源：https://www.cnblogs.com/zhongzw/p/11824821.html
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