打字稿中的import x = require('x')`和`const x = require('x')`之间的区别 [英] Difference between `import x = require('x')` and `const x = require('x')` in typescript

问题描述

在es6中，似乎 import x = require('x')是无效的语法，并且打字稿文档中没有明确的解释.

It seems import x = require('x') is an invalid syntax in es6, and there is no clear explanation in typescript documentation.

推荐答案

Q1: import…= require(...)与 const…= require(...)

在运行时(或一旦编译了代码)，两种语法之间没有区别，第一种语法转换为第二种语法.

Q1: import … = require(…) versus const … = require(…)

At runtime (or once the code is compiled), there is no difference between the two syntaxes, the first one is converted to the second one.

import x = require('x')

此语法特定于TypeScript.常量 x 的类型由在导入的程序包或程序包 @ types/x 中定义的某些类型给出.

This syntax is specific to TypeScript. The constant x is of type given by some typing defined in the imported package or in a package @types/x.

const x = require('x')

这是JavaScript(当然还有TypeScript)中的有效语法.在TypeScript中，常量 x 的类型为 any .

This is a valid syntax in JavaScript and of course in TypeScript. In TypeScript, the constant x is of type any.

从'x'导入x 和 import x = require('x')

import…from ... 的语法来自ES6标准.我建议阅读此介绍关于ES6模块以及如何导入和导出它们.

The syntax import … from … is from the ES6 standard. I suggest to read this introduction to ES6 modules and how to import and export them.

但是，简而言之，语法从'x'导入x 等效于:

But, in short, the syntax import x from 'x' is equivalent to:

import x = require('x').default

(请注意 .default 成员.)

(Notice the .default member.)

ES6标准规定可以将所有导出的成员导入单个命名空间对象模块" .

The ES6 standard states that all exported members can be imported into a single "namespace object module".

然后 import x = require('x')的最接近标准语法是:

Then the closest standard syntax of import x = require('x') is:

import * as x from 'x'

该语法当前可用于TypeScript转译，因为代码已转换为 const…= require(...).

This syntax currently works well with the TypeScript transpilation because the code is converted to a const … = require(…).

但是:该语法仅在标准定义的上下文中使用.因为，当您的代码将使用ES6模块的本机版本时，您将无法以这种方式导入函数或类.

However: This syntax should be used only in the context defined by the standard. Because, when your code will use a native version of ES6 modules, you won't be able to import a function or a class that way.

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