Is it bad practice to require the same module in multiple files in Javascript?

Question

Let’s say I have three files, all of which import a fairly large module. But I’ve divided them because they have different functions. Now each of the JavaScript files needs an initial statement like

const a = require('./') 

Is this considered bad practice?

• Greg Burghardt: Are you using Require.js to import modules?
• Greg Burghardt: When importing files with duplicate imports, do you see more than one request for that resource?
• elbecker: I'm not using Require.js to my knowledge. In my package.json file, I have the module listed under "dependencies". I'm not sure how to view requests for a certain resource.
• Greg Burghardt: Is this code used in a web browser? Server side? Both?
• elbecker: It's a Node.js file, so I think it's server side. I'm new to javascript, by the way

Answer 1

Don't worry about that.

A first require involves a bunch of input/output operations in order to find the matching file and read it into memory. "Any performance impact here will be inconsequential relative to everything else the server is doing" Given that JavaScript modules rarely exceed several megabytes in size, the performance impact of the operation is close to zero.

A second require to the very same module won't even involve that. Since it's already in memory, it is unnecessary to find it on disk or read the actual file. So the performance footprint is even smaller (and much smaller!) than when the module was required for the first time.

If you want to see how it works, create a script which, in a loop, requires the same module many times. Vary the number of iterations and see how it impacts the time spent inside the loop.