Obtaining path in nodejs - javascript

My Directory structure is something as below:
app/
server/
api/
user/
controller.js
images/
image1.jpeg
The problem is when reading image1.jpeg within controller.js I have to use a string like
var imagePath = __dirname + '/../../../images/images1.jpeg';
fs.readFile(imagePath, ()....
now the above works FINE. however what I don't like is this string '/../../../'
is there a better way to access files in the images/ folder ?

You could use path.relative. You'd probably want to save these as constants but you could do the following to make things more readable.
Pass in the path to your current directory as the first parameter and the path to the image itself from the same parent directory (in this case app) and it will return the relative path from the current directory to the image.
// returns '/../../../images/images1.jpeg'
var relativePathToImage = path.relative(
'/app/server/api/user',
'/app/images/images1.jpeg');
var pathToImage = __dirname + relativePathToImage;

Short of passing the path to app/images to the controller, that's about as good as you can do.
You could traverse the module.parent references until module.parent isn't set, if you can safely make assumptions about where your main script is. For example, if your main script is app.js inside app/, you could do something like:
var path = require('path');
var topLevel = module;
while (topLevel.parent)
topLevel = topLevel.parent;
topLevel = path.dirname(topLevel.filename);
var imagesBasePath = path.join(topLevel, 'images');
// ...
fs.readFile(path.join(imagesBasePath, 'images1.jpeg'), ...);

I use an npm module called node-app-root-path to help me manage my paths within the NodeJS application.
See:
https://github.com/inxilpro/node-app-root-path
To obtain the application's root path you would do require('app-root-path');
Example:
global.appRoot = require('app-root-path');
var imagePath = global.appRoot.resolve('server/images');
var img1 = imagePath + '/image1.jpeg';
fs.readFile(img1, ()....
Not sure whether is it a good idea or not but for this case I have stored the appRoot as a global variable and this is so that it will be available anywhere within my NodeJS application stack, even to some of my other NodeJs libraries.
There are many other usages noted in their documentation, have a look and see if it helps you too.

Related

calling a function in another file in javascript using node.js

I have a problem, i am trying to create an object that i can use over and over in a separate javascript file. I have a file called foo.js and another file called boo.js. I want to create the object in boo.js In my server.js file i required foo.js, and it works fine i can access foo.js. I want to be able to access boo.js from foo.js. I keep getting errors when i require boo.js in foo.js and i cant access it. Is There a way to do this?
here is my code
//boo.js
var obj = function () {
return {
data: 'data'
}
}
module.exports = {
obj: obj
}
foo.js
//foo.js
var request = require('request');
var x = require('./modules/boo')
var random= function() {
return x.obj();
}
module.exports = {
random: random
}
If they are in the same directory you will want to require like so var x = require('./boo'). The ./ is relative to the current directory.
they are both in the same directory
In that case, you'll want to remove the modules/ from the path:
var x = require('./boo');
require() is aware of the current script's location and bases relative paths from the script's own parent directory.
The ./ at the start of the path will refer to the same directory as __dirname, which seems to be modules/.
console.log(__dirname);
// "/project-path/modules"
Including modules/ in the path will result in doubling it:
var path = require('path');
console.log(path.resolve(__dirname, './modules/boo'));
// "/project-path/modules/modules/boo"
(Side note: The fs module does not behave the same way. Relative paths for it are based from the current working directory or process.cwd().)

Is it possible to require modules from outside of your project directory without relative paths?

I'm trying to build a local library of JS modules to use in Node projects.
If a new project lives in /Users/me/projects/path/to/new/project/ and my library files are located in /Users/me/projects/library/*.js is there a way to access those files without using a relative path?
In /Users/me/projects/path/to/new/project/app.js you can require foo.js like so:
var foo = require('../../../../../library/foo') and that will work but that's clunky and if files move you'd have to update your relative paths.
I've tried requireFrom and app-module-path with no luck as they are relative to a project root.
Any ideas for how to require files from outside of your project dir?
Thanks in advance!
var librarypath = '/Users/me/projects/library/';
// or if you prefer...
// var librarypath = '../../../../../library/';
var foo = require(librarypath + 'foo.js');
... or dressed up a bit more ...
function requirelib(lib){ return require('/Users/me/projects/library/'+lib+'.js'); }
var foo = requirelib('foo');
var bar = requirelib('bar');
I had the same problem many times. This can be solved by using the basetag npm package. It doesn't have to be required itself, only installed as it creates a symlink inside node_modules to your base path.
const localFile = require('$/local/file')
// instead of
const localFile = require('../../local/file')
Using the $/... prefix will always reference files relative to your apps root directory.
Disclaimer: I created basetag to solve this problem

Process.chdir() has no effect on require

Given the structure directory structure:
.
├── alpha.js
└── foo
└── beta.js
And file contents
alpha.js
module.exports = "alpha"
foo/beta.js
var cwd = process.cwd()
process.chdir('../')
var alpha = require('./alpha.js')
console.log(alpha)
process.chdir(cwd)
From within foo/beta.js. I'd like to be able to trick require into thinking that the current working directory is the project root. The example above does not work when the following is run.
node ./foo/beta.js
However if I switch over the code to within foo/beta.js to the following. Reading the file from the system and passing it to the npm module _eval.
updated foo/beta.js
var path = require('path')
var cwd = process.cwd()
process.chdir(path.join(__dirname, '..'))
var fs = require('fs')
var _eval = require('eval')
var alpha = _eval(fs.readFileSync('./alpha.js'))
console.log(alpha)
process.chdir(cwd)
This does work, which proves it should be possible with require as well. No matter where you run if from it will always require the file. node ./foo/beta.js or cd foo && node ./beta.js
Is there any way that I can prepend or set the directory that require uses from within the file?
From the node.js doc for require():
If the module identifier passed to require() is not a native module,
and does not begin with '/', '../', or './', then node starts at the
parent directory of the current module, and adds /node_modules, and
attempts to load the module from that location.
If it is not found there, then it moves to the parent directory, and
so on, until the root of the file system is reached.
From this, you can see that the current directory is not used in loading modules. The main takeaway here should be that modules paths are relative to the location of the current module. This allows modules to load sub-modules in a self-contained fashion without having to know anything about where the parent is placed in the directory structure.
Here's a work-around function that loads a module file descriptor from the current directory if the filename passed to it does not start with a path separator or a ..
var path = require('path');
function requireCWD(fname) {
var fullname = fname;
if (fname && fname.length &&
!path.isAbsolute(fname) &&
fname.charAt(0) !== '.') {
fullname = path.join(process.cwd(), fname);
}
return require(fullname);
}
Then, any filename you give to requireCWD that is not relative and does not start with a "." will be loaded relative to the current working directory. If you want to allow even "." and ".." to be relative to the current working directory, then you can remove that test for '.' from the function.

process.env.PWD vs process.cwd()

I am using Meteor JS...and within my Meteor app I am using node to query the contents of different directories within the app....
When I use process.env.PWD to query the contents of a folder I get a different result from when I use process.cwd() to query the results of a folder.
var dirServer = process.env.PWD + '/server/';
var dirServerFiles = fs.readdirSync(dirServer);
console.log(dirServerFiles);
//outputs: [ 'ephe', 'fixstars.cat', 'sepl_30.se1', 'server.js' ]
vs
var serverFolderFilesDir = process.cwd() +"/app/server";
var serverFolderFiles = fs.readdirSync(serverFolderFilesDir);
console.log(serverFolderFiles);
//outputs: [ 'server.js' ]
using process.cwd() only shows server.js within the Meteor.
Why is this?
How is process.cwd() different from process.env.PWD?
They're related but not the same thing.
process.env.PWD is the working directory when the process was started. This stays the same for the entire process.
process.cwd() is the current working directory. It reflects changes made via process.chdir().
It's possible to manipulate PWD but doing so would be meaningless, that variable isn't used by anything, it's just there for convenience.
For computing paths you probably want to do it this way:
var path = require('path');
path.resolve(__dirname, 'app/server')
Where __dirname reflects the directory the source file this code is defined in resides. It's wrong to expect that cwd() will be anywhere near that. If your server process is launched from anywhere but the main source directory all your paths will be incorrect using cwd().

Best way to load modules node.js

My project has got many folders and I often load my own modules in node.js in the following way:
var request = require("request"),
config = require("../../../modules/config"),
urls = require("../../../modules/urls");
I sometimes move the folders around and the path changes, so I need to adjust the ../ part manually.
I don't want to move my modules into the node_modules folder, but I'd like to load the modules in the following way:
var request = require("request"),
config = require("config"),
urls = require("urls");
or
var request = require("request"),
config = require("modules/config"),
urls = require("modules/urls");
What are my options?
New Answer:
Relative paths seem to be the simplest choice after all, it allows you to run your script from any location.
var config = require("../../config");
Old answer:
I found out that, while not ideal, there's also the possibility to use process.cwd().
var request = require("request"),
config = require(process.cwd() + "/modules/config");
or, if the process.cwd() is set to a global variable in the main js file
global.cwd = process.cwd();
then
var request = require("request"),
config = require(global.cwd + "/modules/config"),
urls = require(global.cwd + "/modules/urls");
You can try to do the following, based on some conditions
if the scripts are exclusively written for your application, meaning it won't work with any other application, and the scripts don't have any dependencies place them under modules directory and try to create expose a variable such as global.basepath and using path.join to construct the filepath and require it.You could also inject module variable after you require them at the main script of your app.
main.js
var config = require('modules/config.js')(_,mongoose,app);
modules/config.js
module.exports=function(_,mongoose,app){
return function(){
// _,mongoose,app
this.loadConfigVariable..
}
}
if the scripts are not one-files that have separate tests, require other vendor modules in order to be executed then create individual node modules and publish them to a registry for convenience when installing the main application.
Just as express does, there is the main application express and there are modules that express uses such as express-validation which in turn has its own dependencies.
You could add a symlink in node_modules, pointing to wherever your modules are.
For example, add a symlink named "my_modules", referencing '../foo/bar/my_modules'. Then, your requires will look like
var config = require('my_modules/config');
var urls = require('my_modules/urls');

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