Mailmerge pdf in nodejs and hummus-recipe

Question

I'm trying to make a simple mail-merge where recipients information is inserted on top of a template pdf.

The template is 1 page, but the result can be up to several hundred pages.

I have all recipient in array objects, but need to find a way to loop over that and create a unique page for each recipient.

I'm not sure if hummus-recipe is the right tool, so would greatly appreciate any input as to how to do this.

My demo looks like this

const HummusRecipe = require('hummus-recipe')

const recepients = [
    {name: "John Doe", address: "My Streetname 23", zip: "23456", city: "My City"}, 
    {name: "Jane Doe", address: "Another Streetname 56 ", zip: "54432", city: "Her City"} 
    //'.......'
]

const template = 'template.pdf';
const pdfDoc = new HummusRecipe(template, 'output.pdf');

function createPdf(){
    pdfDoc
    .editPage(1)
    .text(recepients[0].name, 30, 60)
    .text(recepients[0].address, 30, 75)
    .text(recepients[0].zip + ' ' + recepients[0].city, 30, 90)
    .endPage()

    //. appendpage(template) - tried versions of this in loops etc., but can't get it to work.

    .endPDF();
}

createPdf();

This obviously only create a single page with recipient[0]. I have tried all sorts of ways to loop over using .appendpage(template), but I can't append and then edit the same page.

Any advice how to move forward from here?

Answer 1

After conversing with the creator of hummus-recipe and others, the solution became somewhat obvious. Its not possible to append a page and then modify it, and its not possible to modify the same page several times.

The solution then is to make the final pdf in two passes. First create a masterPdf where the template is appended in a for loop, save this file and then edit each of those pages.

I have created a working code as shown below. I have made the functions async as I need to run it on lambda an need som control over returns etc. Also this way its possible to save both the tmp-file and final pdf on AWS S3.

The code below takes about 60 seconds to create a 200 page pdf from a 1,6mb template. Any ideas for optimizations will be greatly appreciated.

const HummusRecipe = require('hummus-recipe');
const template = 'input/input.pdf';

const recipients = [
    {name: 'John Doe', address: "My Streetname 23"}, 
    {name: 'Jane Doe', address: "Another Streetname 44"},
    //...etc.
]

async function createMasterPdf(recipientsLength) {
    const key = `${(Date.now()).toString()}.pdf`;
    const filePath = `output/tmp/${key}`;
    const pdfDoc = new HummusRecipe(template, filePath)

    for (i = 1; i < recipientsLength; i++) {
        pdfDoc
        .appendPage(template)
        .endPage()
    }
    pdfDoc.endPDF();
    return(filePath)

}

async function editMasterPdf(masterPdf, recipientsLength) {
    const key = `${(Date.now()).toString()}.pdf`;
    const filePath = `output/final/${key}`;
    const pdfDoc = new HummusRecipe(masterPdf, filePath)

    for (i = 0; i < recipientsLength; i++) {
        pdfDoc
        .editPage(i+1)
        .text(recipients[i].name, 75, 100)
        .text(recipients[i].address, 75, 115)
        .endPage()
    }
    pdfDoc.endPDF()
    return('Finished file: ' + filePath)

}


const run = async () => {
    const masterPdf = await createMasterPdf(recipients.length);
    const editMaster = await editMasterPdf(masterPdf, recipients.length)
    console.log(editMaster)
}

run()