How to pass return value from one `npm run script.js` as a parameter to another `npm run script2.js`?

Question

Is there a way to implement it in scripts in package.json somehow without using third-party components?

Answer 1

I'm not sure this is the best solution but I couldn't come up with something better yet. Since I was looking for an approach for Windows console I've checked it only in there, but I think it should work in Linux shell too.

So, we will have 2 JavaScript files:

1. send-param.js: should send (return) a string param
2. read-param.js: should get that string param as an argument

Both these JS files should be run from scripts of package.json. The technique itself is pretty simple: the send-param.js writes a string value to stdout whereas read-param.js then gets it as an argument. The main problem was how to "convert" stdout into an argument for the read-param.js script.

To write something to stdout we can use console.log and that's what send-param.js actually does:

console.log("Hello World!");

Next, we want to run read-param.js to get the "Hello World!" string from arguments but it seems to be impossible to do it directly in Windows console. So I had to use an interim operation to write that argument from stdout to auxiliary file (I just named it '1.txt') and here it's done in the first part of the script:

node send-param.js > 1.txt

Now we have "Hello World!" in the '1.txt' file and we have to send it somehow as a parameter the the read-param.js script. Again, I couldn't find how to do it directly in Windows console and used a variable which I called 'ARG':

set /p ARG=<1.txt

Finally, we can use the 'ARG' variable as an argument for out read-param.js script:

"node read-param.js %ARG%"

The first thing that came to my mind was to execute all commands in one-line-script like this:

"send-param.js > 1.txt && set /p ARG=<1.txt && node read-param.js %ARG%"

but it wouldn't work since it's required to run set as a separate command (see why).

In read-param.js we just read the first argument as process.argv[2] (Node.js reserves the 0 and 1-st ones for its own arguments).

---

Here is the final working example:

send-param.js:

console.log("Hello World!");

read-param.js:

const argument = process.argv[2];

if (!argument)
    console.log('An argument is required.');
else
    console.log(`Argument: '${argument}'`);

package.json:

"scripts": {
  "send": "node send-param.js > 1.txt && set /p ARG=<1.txt && npm run read",
  "read": "node read-param.js %ARG%",
}

Now run the npm run send command and you will get: Argument: 'Hello World!'