TypeScript 没有等效于 LINQ 的语言集成天然查询方面?不能在 TypeScript 中写入如下 LINQ 语句typescript
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var
adultUserNames =
from
u
in
users
where
u.Age >= 18
select
u.Name;
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可是，位于 LINQ 核心的 iE6<T>扩展方法在 TypeScript 中具备等效项（或能够模拟）。数组
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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
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Aggregate
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// C#
var
leftToRight = users.Aggregate(initialValue, (a, u) =>
/* ... */
);
// TypeScript
const
leftToRight = users.reduce((a, u) =>
/* ... */
, initialValue);
const
rightToLeft = users.reduceRight((a, u) =>
/* ... */
, initialValue);
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All
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// C#
var
allReady = users.All(u => u.IsReady);
// TypeScrip
tconst allReady = users.every(u => u.isReady);
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Any
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// C#
var
isDirty = users.Any(u => u.IsDirty);
// TypeScript
const
isDirty = users.some(u => u.isDirty);
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Append
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// C#
var
allUsers = users.Append(oneMoreUser);
// TypeScript
const
allUsers = [ ...users, oneMoreUser ];
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Average
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// 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;
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Cast
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// 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：在语义上不一样。C# 版本引起异常若是没法强制转换为键入 Person 的任何用户。
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Concat
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// C#
var
allUsers = users.Concat(moreUsers);
// TypeScript
const
allUsers = [ ...users, ...moreUsers ];
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Contains
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// C#
var
hasAdmin = users.Contains(admin);
// TypeScript
const
hasAdmin = users.includes(admin);
// Use a polyfill for IE support
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Count
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// C#
var
n = users.Count();
// TypeScript
const
n = users.length;
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DefaultIfEmpty
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// C#
var
nonEmptyUsers = Enumerable.DefaultIfEmpty(users);
// TypeScript
const
nonEmptyUsers = users.length ? users : [
null
];
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Distinct
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// C#
var
uniqueNames = users.Select(u => u.Name).Distinct();
// TypeScript
const
uniqueNames = Object.keys(users.map(u => u.name).reduce((un, u) => ({ ...un, n }),{}));
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ElementAt
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// 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];
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ElementAtOrDefault
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// C#
var
nth = users.ElementAtOrDefault(n);
// TypeScript
const
nth = users[n];
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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>();
// TypeScript
const
noUsers: User[] = [];
const
noUsers = []
as
User[];
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Except
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// 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）
);
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First
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// C#
var
first = users.First();
// TypeScript
if
(users.length < 1) {
throw
new
Error(
'Sequence contains no elements'
);
}
const
first = users[0];
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FirstOrDefault
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// C#
var
first = users.FirstOrDefault();
// TypeScript
const
first = users[0];
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List.ForEach
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// C#
users.ToList().ForEach(u =>
/* ... */
);
// TypeScript
users.forEach(u =>
/* ... */
);
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GroupBy
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// C#
var
usersByCountry = users.GroupBy(u => u.Country);
// TypeScript
const
usersByCountry = users.reduce((ubc, u) =>
({
...ubc,
[u.country]: [ ...(ubc[u.country] || []), u ],}),
{});
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Intersect
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// C#
var
targetUsers = usersWhoClicked.Intersect(usersBetween25And45);
// TypeScript
const
targetUsers = usersWhoClicked.filter(u => usersBetween25And45.includes(u)
// Use a polyfill for IE support);
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Last
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// C#
var
last = users.Last();
// TypeScrip
tif (users.length < 1) {
throw
new
Error(
'Sequence contains no elements'
);
}
const
last = users[users.length - 1];
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LastOrDefault
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// C#
var
last = users.LastOrDefault();
// TypeScript
const
last = users[users.length - 1];
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Max
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// 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);
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Min
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// 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);
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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
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OrderBy / ThenBy
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// 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
}
);
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Reverse
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// C#
var
backwards = users.Reverse();
// TypeScript
const
backwards = users.reverse();
// Caution: users is also reversed! 原数组也翻转了
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Select
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// C#
var
names = users.Select(u => u.Name);
// TypeScript
const
names = users.map(u => u.name);
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SelectMany
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// C#
var
phoneNumbers = users.SelectMany(u => u.PhoneNumbers);
// TypeScript
const
phoneNumbers = users.reduce((pn, u) => [ ...pn, ...u.phoneNumbers ], []);
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Single
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// 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];
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SingleOrDefault
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// C#
var
user = users.Single();
// TypeScript
const
user = users[0];
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Skip
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// C#
var
otherUsers = users.Skip(n);
// TypeScript
const
otherUsers = users.filter((u, i) => i >= n);
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SkipWhile
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// C#
var
otherUsers = users.SkipWhile(predicate);
// TypeScript
let
i = 0;
while
(i < users.length && predicate(users[i++]));
const
otherUsers = users.slice(i - 1);
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Sum
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// 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);
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Take
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// C#
var
otherUsers = users.Take(n);
// TypeScript
const
otherUsers = users.filter((u, i) => i < n);
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TakeWhile
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// C#
var
otherUsers = users.TakeWhile(predicate);
// TypeScript
let
i = 0;
while
(i < users.length && predicate(users[i++]));
const
otherUsers = users.slice(0, i - 1);
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Union
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// 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
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Where
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// C#
var
adults = users.Where(u => u.Age >= 18);
// TypeScript
const
adults = users.filter(u => u.age >= 18);
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Zip
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// 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], });
}
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水平有限，请你们见谅，翻译的有误，请指出。谢谢post
原文地址 https://decembersoft.com/posts/typescript-vs-csharp-linq/ui