什么是Node.js中的declare var？ [英] What is declare var in Node.js?

问题描述

在此nodejs代码中，

in this nodejs code,

declare var process: NodeJS.Process;
declare var global: NodeJS.Global;
declare var console: Console; 
declare var __filename: string;
declare var __dirname: string;

...

什么是'declare var'和'var'之间的区别？

What's the difference between 'declare var' and 'var'?

当我查看谷歌搜索时，我得到运行时一词。

When I look up on the googling, I get the word runtime.

wiki说运行时是计算机程序运行时的一个操作....

wiki says runtime is an operation while a computer program is running....

但我无法理解。

和第1行，process之后的：是什么意思，然后是NodeJS.Process？

and line 1, what does it mean by ":" after "process" and then "NodeJS.Process"?

这是什么意思process等于NodeJS.Process？

Is that mean "process" is equal "NodeJS.Process"?

也是第4行，__ filename之后的：是什么意思，然后是string？

also line 4, what does it mean by ":" after "__filename" and then "string"?

这是否意味着__filename等于string？

Is that mean "__filename" is equal "string"?

谢谢你。

推荐答案

使用时：

var process: NodeJS.Process;

您正在创建名为 process 的变量（没有定义值）并告诉TypeScript编译器为分配强制执行 NodeJS.Process 类型。

You are creating a variable named process (with no value defined) and telling the TypeScript compiler to enforce the NodeJS.Process type for assignments.

当你添加声明：

declare var process: NodeJS.Process;

你告诉TypeScript编译器已经一个名为<的变量code>进程，类型为 NodeJS.Process 。当你有编译器不知道的源引入的变量时，这很有用。

You are telling the TypeScript compiler that there is already a variable named process with the type NodeJS.Process. This is useful when you have variables introduced by sources that the compiler is not be aware of.

参见 TypeScript手册中的声明文件。

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