It seems that the code works but doesn’t scale too well.
It’s possible that by performing all operations in parallel, javascript’s Garbage Collection (GC) isn’t given the opportunity to clear intermediate objects, and an oversized heap causes the crash.
Performing the operations in series may have a positive effect. The code is simply derived from the code in the question.
First, an adaptor function, which promisifies html2canvas() :
function html2canvasAsync(element) {
return new Promise(function(resolve, reject) {
html2canvas(element, {
onrendered: function (canvas) {
resolve(canvas.toDataURL('image/png'));
}
});
});
};Now call divNamesForPDF.reduce(…) to serialize the asynchronous operations and progressively add to the jsPDF doc :
function GeneratePDFforCharts(divNamesForPDF) {
if (window.Promise) {
var doc = new jsPDF('l', 'mm', [297, 210], true); //true is set for pdf compression
return divNamesForPDF.reduce(function(p, name, i) {
return p.then(function(pageNumber) {
return html2canvasAsync($(name).get(0)) // or `document.getElementById(name)` ?
// return html2canvasAsync(document.getElementById(name)) // possibly?
.then(function(canvas) {
if (isOdd(i)) { // odds
doc.addImage(canvas, 'PNG', 10, 105, 270, 100, null, 'FAST'); //x, y, width, height - FAST is used for png compression
doc.text(140, 207, pageNumber.toString()); //x, y, text
pageNumber++;
} else { // evens
if (i > 0) {
doc.addPage();
}
doc.addImage(canvas, 'PNG', 10, 5, 270, 100, null, 'FAST');
}
return pageNumber;
}).catch(function(e) {
// Error handling is a good idea
console.log(e);
doc.text(35, 25, e.message); // possibly add the error message to doc
});
});
}, Promise.resolve(1)) // starter promise resolved with page number 1
.then(function() {
doc.save('IEA_Global_MonthlyStocks_Analytics.pdf');
});
}
}