Test for chartjs-node npm module which checks if a file is ready after writing

chartjs-node-test.js

const ChartjsNode = require('chartjs-node');
const fs = require('fs');
const tmp = require('tmp');

charts = {
    drawLineChart: function(options,onFinish) {
        var width = options.width ? options.width : 700;
        var height = options.height ? options.height : 400;

        delete options.width, options.height;

        var chartNode = new ChartjsNode(width, height);

        var filename = tmp.tmpNameSync({template: '/tmp/tmp-XXXXXX.png'});

        return chartNode.drawChart(options).then(() => {
            return chartNode.getImageBuffer('image/png');
        }).then(buffer => {
            Array.isArray(buffer) // => true 
            // as a stream 
            return chartNode.getImageStream('image/png');
        })
        .then(streamResult => {
            // using the length property you can do things like 
            // directly upload the image to s3 by using the 
            // stream and length properties 
            //streamResult.stream // => Stream object 
            //streamResult.length // => Integer length of stream 
            // write to a file 
            return chartNode.writeImageToFile('image/png', filename);
        })
        .then(() => {
            if(typeof onFinish == 'function') {
                onFinish.call(this,filename);
            }
        })
    }
}

charts.drawLineChart(chartJsOptions,function(filename) {
    fs.stat(filename, function(err, stat) {
    if(err == null) {
        console.log('Starting upload ' + filename);
        // upload code goes here
    } else if(err.code == 'ENOENT') {
        console.log('System reports ' + filename + ' does not exist.');
    }
    else {
        console.log('Some other error: ', err.code);
    }
    }.bind(this));
});