CODEWITHSUNDEEP
node.jsmodulereload
az1mov
az1mov

Reputation: 469

Node.js: how to reload module

I am new to NodeJS so probably I am doing some mistakes.

I have written a bunch of code in an external file called myapp. I start NodeJS for windows and from the interpreter window I type:

var myapp = require('d:/myapp.js');

then I can use my functions and variables in the external module.

The problem is that if I update the code in myapp then the interpreter does not re-read the file and it uses the old version.

Now, is this normal in the first place? How to work around this problem?

P.S.: I have spent hours in internet and searched in many forums including this. It was more confusing then anything else.

Thanks.

Upvotes: 36

Views: 31899

Answers (3)

mihai
mihai

Reputation: 38543

There are some answers here as suggested in the comments.

However they are not REPL friendly, and might even use extra modules.

Here is a one line solution that you can paste in your REPL, inspired by the discussion on the other question:

function nocache(module) {require("fs").watchFile(require("path").resolve(module), () => {delete require.cache[require.resolve(module)]})}

The function will delete your module from the cache each time the file changes. To use it, just paste it in the REPL, call nocache("d:/myapp.js"), then use require normally.

> function nocache(module) {require("fs").watchFile(require("path").resolve(module), () => {delete require.cache[require.resolve(module)]})}
> nocache("d:/myapp.js");
> var myapp = require("d:/myapp.js");
......
> myapp = require("d:/myapp.js");
....

Upvotes: 33

Lee
Lee

Reputation: 31040

I solved this by adding the following above the require statements:

Object.keys(require.cache).forEach(function(key) { delete require.cache[key] })

Taken from @Dancrumb's comment here

Upvotes: 7

codechimp
codechimp

Reputation: 1547

The other answers (in duplicate and by @mihai) are all correct, but the most direct answer to this specific example, is

delete require.cache['d:/myapp.js'];

The module is cached in require.cache keyed to the full filename. In this particular case, the full filename (i.e. d:/myapp.js) was used to load, and so the solution to the problem is very straight forward.

In most cases, however, the full filename is not used or even known. For example, require('fs') would be used to load the filesystem module, but the developer is as a loss to the full and proper filename. As such, require.resolve('fs') will return the filename used as key to cache the module.

Upvotes: 18

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