TypeScript vs. C#: LINQ

TypeScript 沒有等效於 LINQ 的語言集成自然查詢方面?不能在 TypeScript 中寫入以下 LINQ 語句

var adultUserNames = from u in users where u.Age >= 18 select u.Name;

但是，位於 LINQ 核心的 iE6擴展方法在 TypeScript 中具有等效項（或可以模擬）。

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);

// TypeScript
const 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();

// 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：在語義上不同。C# 版本引發異常如果無法強制轉換為鍵入 Person 的任何用戶。

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();//?.NET 4.0 沒找到 找到的是DefaultIfEmpty
//var noUsers = IEnumerable.DefaultIfEmpty();

// 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();//根據類型刷新元素

// TypeScript
// No equivalent 無等效項

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! 原數組也翻轉了

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#

vr 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，請大家見諒，翻譯的有誤，請指出。謝謝