node.js – Nodejs: deleting files after all operations are completed

You aren’t waiting for res.download() to complete so you’re trying to delete ./uploads/output.pptx before you’ve finished sending it to the client. res.download() takes an optional callback that will tell you when it’s complete or you can promisify it so that you can then await it and then only call deleteFiles() when res.download() has finished.

For example, you could do this:

@Post(':id/export')
async potrfolioExport(
    @Body() files: string[],
    @Param('id') id: any,
    @Res() res: Response
) {

    const paths = files.map((elem) => `./uploads/${elem}.pptx`);

    try {
        await this.filesService.downloadFiles(files);
        await this.filesService.downloadAdditionalFile('template.pptx');
        await this.mergePres(paths);
        res.download(`./uploads/output.pptx`, (error) => {
            if (error) {
                if (!res.headersSent) {
                    res.status(500).json({ message: error.message, error: error });
                }
            }
            this.filesService.deleteFiles([...paths, './uploads/template.pptx', './uploads/output.pptx']);
        });

    } catch (error) {
        console.error("Error: ", error.body);
        await this.filesService.deleteFiles([...paths, './uploads/template.pptx', './uploads/output.pptx']);
        res.status(500).json({ message: error.message, error: error });
    }    
}

Or, here’s a version where you promisify res.download() and consolidate error handling:

import { promisify } from 'node:util';

@Post(':id/export')
async potrfolioExport(
    @Body() files: string[],
    @Param('id') id: any,
    @Res() res: Response
) {

    const paths = files.map((elem) => `./uploads/${elem}.pptx`);

    try {
        await this.filesService.downloadFiles(files);
        await this.filesService.downloadAdditionalFile('template.pptx');
        await this.mergePres(paths);

        res._download = promisify(res.download);
        await res._download((`./uploads/output.pptx`);
    } catch (error) {
        console.error("Error: ", error.body);
        if (!res.headersSent) {
            res.status(500).json({ message: error.message, error: error });
        }
    } finally {
        this.filesService.deleteFiles([...paths, './uploads/template.pptx', './uploads/output.pptx']).catch(err => {
            console.error(err);    
        });    
    }    
}