node.js 节点 __dirname 未定义
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node __dirname not defined
提问by topskip
From the node manual I see that I can get the directory of a file with __dirname, but from the REPL this seems to be undefined. Is this a misunderstanding on my side or where is the error?
从节点手册中我看到我可以使用 获取文件的目录__dirname，但是从 REPL 中这似乎是未定义的。这是我的误解还是错误在哪里？
$ node
> console.log(__dirname)
ReferenceError: __dirname is not defined
at repl:1:14
at REPLServer.eval (repl.js:80:21)
at Interface.<anonymous> (repl.js:182:12)
at Interface.emit (events.js:67:17)
at Interface._onLine (readline.js:162:10)
at Interface._line (readline.js:426:8)
at Interface._ttyWrite (readline.js:603:14)
at ReadStream.<anonymous> (readline.js:82:12)
at ReadStream.emit (events.js:88:20)
at ReadStream._emitKey (tty.js:320:10)
回答by qiao
__dirnameis only defined in scripts. It's not available in REPL.
__dirname仅在脚本中定义。它在 REPL 中不可用。
try make a script a.js
尝试编写脚本 a.js
console.log(__dirname);
and run it:
并运行它：
node a.js
you will see __dirnameprinted.
你会看到__dirname打印出来的。
Added background explanation: __dirnamemeans 'The directory of this script'. In REPL, you don't have a script. Hence, __dirnamewould not have any real meaning.
添加了背景说明：__dirname表示“此脚本的目录”。在 REPL 中，您没有脚本。因此，__dirname不会有任何实际意义。
回答by c24w
Building on the existing answers here, you could define this in your REPL:
基于此处现有的答案，您可以在 REPL 中定义它：
__dirname = path.resolve(path.dirname(''));
Or:
或者：
__dirname = path.resolve();
Or @Jthorpe's alternatives:
或@Jthorpe 的替代方案：
__dirname = process.cwd();
__dirname = fs.realpathSync('.');
__dirname = process.env.PWD
回答by t-reksio
In ES6 use:
在 ES6 中使用：
import path from 'path';
const __dirname = path.resolve();
also available when node is called with --experimental-modules
当节点被调用时也可用 --experimental-modules
回答by jeremywoertink
As @qiao said, you can't use __dirnamein the node repl. However, if you need need this value in the console, you can use path.resolve()or path.dirname(). Although, path.dirname()will just give you a "." so, probably not that helpful. Be sure to require('path').
正如@qiao 所说，您不能__dirname在节点 repl 中使用。但是，如果您需要在控制台中使用此值，则可以使用path.resolve()或path.dirname()。虽然，path.dirname()只会给你一个“。” 所以，可能没有那么有帮助。一定要require('path')。
回答by Desire Kaleba
I was also trying to join my path using path.join(__dirname, 'access.log')but it was throwing the same error.
我也试图加入我的路径，path.join(__dirname, 'access.log')但它抛出了同样的错误。
Here is how I fixed it:
这是我修复它的方法：
I first imported the pathpackage and declared a variable named __dirname, then called the resolvepathmethod.
我首先导入了路径包并声明了一个名为 的变量__dirname，然后调用了resolve路径方法。
In CommonJS
在 CommonJS 中
var path = require("path");
var __dirname = path.resolve();
In ES6+
在 ES6+ 中
import path from 'path';
const __dirname = path.resolve();
Happy coding.......
快乐编码......
回答by Joel M Ward
Seems like you could also do this:
好像你也可以这样做：
__dirname=fs.realpathSync('.');
of course, dont forget fs=require('fs')
当然，不要忘记 fs=require('fs')
(it's not really global in node scripts exactly, its just defined on the module level)
（它在节点脚本中并不是真正全局的，它只是在模块级别定义的）
回答by Siva Prakash
Though its not the solution to this problem I would like to add it as it may help others.
虽然它不是这个问题的解决方案，但我想添加它，因为它可能会帮助其他人。
You should have two underscoresbefore dirname, not one undersore(__dirnamenot _dirname).
你应该在 dirname 之前有两个下划线，而不是一个 undersore( __dirnamenot _dirname)。
回答by Pawel
I was running a script from batch file as SYSTEM user and all variables like process.cwd(), path.resolve()and all other methods would give me path to C:\Windows\System32 folder instead of actual path. During experiments I noticed that when an error is thrown the stack contains a true path to the node file.
我正在以 SYSTEM 用户和所有变量（如 ）的身份从批处理文件运行脚本process.cwd()，path.resolve()所有其他方法都会为我提供 C:\Windows\System32 文件夹的路径，而不是实际路径。在实验期间，我注意到当抛出错误时，堆栈包含节点文件的真实路径。
Here's a very hacky way to get true path by triggering an error and extracting path from e.stack. Do not use.
这是通过触发错误并从 e.stack 中提取路径来获得真实路径的一种非常hacky 的方法。不使用。
// this should be the name of currently executed file
const currentFilename = 'index.js';
function veryHackyGetFolder() {
try {
throw new Error();
} catch(e) {
const fullMsg = e.stack.toString();
const beginning = fullMsg.indexOf('file:///') + 8;
const end = fullMsg.indexOf('\/' + currentFilename);
const dir = fullMsg.substr(beginning, end - beginning).replace(/\//g, '\');
return dir;
}
}
Usage
用法
const dir = veryHackyGetFolder();
回答by vikky singh
sometimes we make a file with .js extension and add consol.log(_dirname); but we face errors, we are in a hurry, so we forget to add one more underscore before the "dirname" so we face reference error.correct syntax is consol.log(__dirname);
有时我们创建一个扩展名为 .js 的文件并添加 consol.log(_dirname); 但是我们遇到了错误，我们很着急，所以我们忘记在“dirname”之前再添加一个下划线，因此我们面临引用错误。正确的语法是consol.log(__dirname);
