Best way to evaluate javascript source code module with node.js

Question

With node, I transpile a typescript tsx file int javascript. Then I need to call a function that is described in that javascript code. ES6 modules are used.

I use

writeFileSync('./temp/page1.js', js) // js is the module source code
import page from '../temp/page1.js'

page is here the default export which is a function that I want to call.

That works fine but I wonder if there is a better way to call the function inside the module source code? A way that avoids saving the source code into a temporary file.

eval would not be a security concern, but I think it would not give me the default export, modules are not considered in this old function.

Maybe something node related?

I found https://www.npmjs.com/package/node-eval which would avoid the file saving, although it still requires a filename, which causes some brittleness in my code.

node:module node:vm

are maybe promising, looking at https://github.com/node-eval/node-eval/blob/master/index.js but I have not yet figured out if and how.

Similar, but more related to require: Load node.js module from string in memory

https://github.com/floatdrop/require-from-string did not work either

all the variants with node:vm like

import vm from 'node:vm'
let context = vm.createContext({}, {name:"temp1.mjs"})
vm.runInContext(js, context, {filename: "temp2.mjs"})

result in "Cannot use import statement outside a module"

in node. In the end this would be a bundler plugin, say a snowpack plugin. — citykid
– citykid, Commented Jul 20, 2021 at 23:22
rtm vm: nodejs.org/api/vm.html - depends on your usage, you are probably looking for vm.runInNewContext, it seems you essentially want to execute what's in the js var in a safe way, which you can do with vm module, either in context, new content or this context. — Lawrence Cherone
– Lawrence Cherone, Commented Jul 20, 2021 at 23:55

citykid · Accepted Answer · 2021-07-21 00:34:36Z

1

The best way would be nodes vm.Module class

https://nodejs.org/api/vm.html#vm_module_evaluate_options

but that is in draft stage and behind feature flags.

answered Jul 21, 2021 at 0:34

citykid

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