Loading Javascript from a string in Node with Needle

In this guide, we'll show you how to load custom javascript code as a given string when converting an HTML document to PDF using PDFShift's API. This allows you to add custom JS to your page to customize the output of your generated PDF.

It can be interesting to be able to set a custom JS value to adjust the rendering of your page specifically when exporting the document to PDF. This allows you to keep a standard look and feel to your users, but adjust some areas when sending that same document to PDFShift to get back a PDF.

const needle = require('needle');
const fs = require('fs');

// You can get an API key at https://pdfshift.io
api_key = 'sk_xxxxxxxxxxxx'

params = {
    source: 'https://www.example.com',
    javascript: 'document.querySelector("h1").style.color = "red";'
}

needle.post(
    'https://api.pdfshift.io/v3/convert/pdf',
    params,
    {
        username: 'api',
        password: apiKey,
        json: params,
    },
    function(err, resp) {
        if (err) throw err;

        // Write the response body to a local file
        fs.writeFileSync('result.pdf', resp.body, 'binary');

        console.log('The PDF document was generated and saved to result.pdf');
    }
)

The javascript parameter accepts either a string or a URL. It will be used as the javascript for the page when converting it to PDF. This allows you to set a custom JS value to adjust the rendering of your page specifically when exporting the document to PDF.