How to prepend text to a file as an npm script command

Question

I'm writing a bookmarklet. I need to prepend "javascript:" to the compiled, minified JavaScript. I'm looking for a way to accomplish this using an NPM package.json script.

{ 
    "scripts": {
        "oar:transpile-typescript": "tsc --target es6  --lib dom,es6 ./OarBookmarklet/Oar.ts",
        "oar:minify-javascript": "jsmin -o ./OarBookmarklet/oar.min.js ./OarBookmarklet/oar.js",
        "oar:prepend-javascript": "[??? prepend `javascript:` to minified JavaScript ???]",
        "oar": "run-s oar:transpile-typescript oar:minify-javascript oar:prepend-javascript",
        "build": "run-s oar"
    }
}

Community · Accepted Answer · 2020-06-20 09:12:55Z

For a cross-platform solution utilize node.js and it's builtin fs.readFileSync(...) and fs.writeFileSync(...). This way it doesn't matter which shell your npm script runs in (sh, cmd.exe, bash, bash.exe, pwsh, ... )

To achieve this consider either of the following two solutions - they're essentially the same just different methods of application.

Solution A. Using a separate node.js script

Create the following script, lets save it as prepend.js in the root of the project directory, i.e. at the same level as where package.json resides.

prepend.js

const fs = require('fs');
const filepath = './OarBookmarklet/oar.min.js';
const data = fs.readFileSync(filepath);
fs.writeFileSync(filepath, 'javascript:' + data);

package.json

Define the oar:prepend-javascript npm script in package.json as follows::

"scripts": {
  ...
  "oar:prepend-javascript": "node prepend",
  ...
},

_{Note: Above node.js invokes the script and performs the required task. If you choose to save prepend.js in a different directory than the aforementioned then ensure you define the correct path to it, i.e. "oar:prepend-javascript": "node ./some/other/path/to/prepend.js"}

Solution B. Inline the node.js script in package.json

Alternatively, you can inline the content of prepend.js in your npm script, therefore negating the use of a separate .js file.

package.json

Define the oar:prepend-javascript script in package.json as follows:

"scripts": {
  ...
  "oar:prepend-javascript": "node -e \"const fs = require('fs'); const fp = './OarBookmarklet/oar.min.js'; const d = fs.readFileSync(fp); fs.writeFileSync(fp, 'javascript:' + d);\""
  ...
},

_{Note: Here the nodejs command line option -e is utilized to evaluate the inline JavaScript.}

ottomeister · Accepted Answer · 2019-03-31 22:22:42Z

1

If this is running on something Unix-like then:

(printf 'javascript:' ; cat ./OarBookmarklet/oar.min.js) > ./OarBookmarklet/oar.bm.min.js

should do the job.

Edit in response to OP's comment:

My execution environment is Windows, ...

In that case you should be able to use:

(set /p junk="javascript:" <nul & type ./OarBookmarklet/oar.min.js) > ./OarBookmarklet/oar.bm.min.js

The set /p ... <nul weirdness is a way to get some text sent to stdout without a newline being appended to it.

edited Mar 31, 2019 at 22:22

answered Mar 30, 2019 at 0:16

ottomeister

5,8582 gold badges26 silver badges27 bronze badges

3 Comments

CalvinDale Over a year ago

My execution environment is Windows, VS Code, PowerShell console.

CalvinDale Over a year ago

I had to use double-backslashes for the path: "(set /p junk=\"javascript:\" <nul & type .\\OarBookmarklet\\oar.min.js) > .\\OarBookmarklet\\oar.bm.min.js"

RobC Over a year ago

Is is possible to prepend the text to the original oar.min.js without having to create another file, i.e. oar.bm.min.js ?

Collectives™ on Stack Overflow

How to prepend text to a file as an npm script command

2 Answers 2

Solution A. Using a separate node.js script

Solution B. Inline the node.js script in package.json

Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Solution A. Using a separate node.js script

Solution B. Inline the node.js script in package.json

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related