How to get the number of pages of a .PDF uploaded by user?

Question

I have a file input, and before \"uploading\" i need to calculate the number of pages of that .pdf in JAVASCRIPT (eg. JQuery...)

Answer 1

and a pure javascript solution:

var input = document.getElementById("files");
var reader = new FileReader();
reader.readAsBinaryString(input.files[0]);
reader.onloadend = function(){
    var count = reader.result.match(/\/Type[\s]*\/Page[^s]/g).length;
    console.log('Number of Pages:',count );
}