Pptxgenjs: Can't create multiple presentations in node

[daynedavis]

I am requiring pptx via var pptx = require('pptxgenjs') within a function called by a route on my node server, but when I hit the endpoint multiple times slides are added to the same presentation (first time it returns a ppt with 4 slides, second time one with 8 slides). Changing module.exports to be PptxGenJs in pptxgen.js and then requiring pptx = new (require('pptxgenjs'))() allowed me to get separate instances. Is this a bug or is there a way to get multiple instances in node without making that change?

[gerbendekker]

That would be nice, having the same issue here.
Needed to restart the electron app for each new pptx.
What I did is creating a new public function 'newFile' but don't know this is appropriate.

this.newFile = function newFile() {
    gObjPptx = {};
    gObjPptx.author = 'PptxGenJS';
    gObjPptx.company = 'PptxGenJS';
    gObjPptx.revision = '1';
    gObjPptx.subject = 'PptxGenJS Presentation';
    gObjPptx.title = 'PptxGenJS Presentation';
    gObjPptx.fileName = 'Presentation';
    gObjPptx.fileExtn = '.pptx';
    gObjPptx.pptLayout = LAYOUTS['LAYOUT_16x9'];
    gObjPptx.slides = [];
}

[gitbrent]

Hi @daynedavis @gerbendekker ,

Thanks for the question.

I've added a new section to the README that covers this very issue:
Saving a Node.js Presentation

See also: Issue #38

[gerbendekker]

How does this cover the NodeJs usecase of above?
Can't 'new' the PptxGenJS class because it isn't exposed.

var pptx = require("pptxgenjs");

[daynedavis]

@gitbrent like @gerbendekker said I'm not able use new in NodeJs since the class is not exposed.

[gitbrent]

Hi @daynedavis @gerbendekker,

Ack! I spaced out and used the wrong code. Sorry about that.

It should've been pptx = require("pptxgenjs"); and i've corrected the README as well.

Does this work for you guys, or would a more formal method like clearPresentation() (something that would remove all the Slides from the current Presentation) be preferable?

[gerbendekker]

Now we are back where we started.
Let me write some more context about the issue in NodeJs:

Problem

let pptx = require('pptxgenjs');
let slide1 = pptx.addNewSlide();
let slide2 = pptx.addNewSlide();

pptx = require('pptxgenjs');
// How many slides does pptx have?

The answer is 2, because require('pptxgenjs') returns the same (singleton) instance.

Solution
What I would expect in 'pptxgen.js' and described by @daynedavis:

module.exports = PptxGenJS;

Then we can write:

let PptxGenJS = require('pptxgenjs');
let pptx = new PptxGenJS();
let slide1 = pptx.addNewSlide();
let slide2 = pptx.addNewSlide();

pptx = new PptxGenJS();
// Yeay a new instance.

But that is a breaking change.
For the development roadmap of version 2.0 I would advise to export the class instead of an instance.

Thinking forward...
What use case would clearPresentation() have in 2.0? I would use new PptxGenJS().
But I can imagine a use case for removeSlide().
My advise would be adding a removeSlide(pageNumber) to version 1 and we can iterate to clear the presentation.

[LiranBri]

I fixed it in the current version by deleting the module from the cache before requiring again:

  delete require.cache[require.resolve('pptxgenjs')]
  let pptx = require('pptxgenjs')

[labriola]

Here is a much cleaner work around:

var pptxgenjs = require('pptxgenjs');
var pptx = new pptxgenjs.constructor();
...
pptx.save(name);

const pptx2 = new pptxgenjs.constructor();
...
pptx2.save(name);

Using the constructor property of the function will let you build new objects at will.

[dtabolich]

Any news guys?

[gitbrent]

Hi @dtabolich,

Other than the newer posts above, no. The factory method will be updated in 2.0 as it's a breaking change, until then work-arounds are all that's available. :-(

[labriola]

@gitbrent let me know your thoughts on this. It's not ideal but it would solve the issue in a way that node users should expect and keep things compatible.

[gitbrent]

Hi All,

UPDATE: A fix for this issue is now checked into the 2.0.0 codebase!

Individual, singleton instances of PptxGenJS are now created using the standard Node syntax:

var PptxGenJS = require("pptxgenjs");
let pptx = new PptxGenJS();

If any of you would care to demo it and provide feedback, i'd appreciate it. :-)

New Node Examples:

• The examples/node-demo.js file now creates 2 separate Presentations to demo the new functionality.

See README section for more:

• Saving Multiple Presentations

[gitbrent]

Version 2.0.0 has been released and this issue is now fixed.

Thank you all for your feedback.