Asynchronous call handling in javascript

Question

I am trying to call a function saveBadge() and getting the value of the function to use in the for loop.But every time I am getting the value from an array where I am converting the div tag to Image. but every time I am getting the last value. How do I handle the Asynchronous call?.

    for(var j=0;j<anarray.length;j++)
    {
        var json=JSON.parse(anarray[j]);
        // adding in badge image
        alert(anarray[j]);

        var imgTem=json['regId']['image'];
        var imgFin=imgTem.replace("dataimage","data:image").replace("base64",";base64,");              


        $("#name").text(json['regId']['fname']+" "+json['regId']['lname']);  // User name
        var imgTem=json['regId']['image'];
        var imgFin=imgTem.replace("dataimage","data:image").replace("base64",";base64,");     
        $("#image").attr("src",imgFin);                                     // User Image
        $("#gender").text(json['regId']['gender']);                         // User Gender

        //QRcode generator
        var qrcode = json['badgeId'];                                       // User QRcode
        var qr = new QRious({
            element: document.getElementById('qrcanvas'),
            value: qrcode,
            background: 'white', // background color
            foreground: 'black', // foreground color
            level: 'L', // Error correction level of the QR code (L, M, Q, H)
            mime: 'image/jpeg', // MIME type used to render the image for the QR code
            size: 120 // Size of the QR code in pixels.
        });         
        //qr.toDataURL("jpeg"); // Generates a base64 encoded data URI for the QR code. 
       savebadge();  
        var bdgImg = localStorage.getItem("bdgImg");

        var qrjson = JSON.parse(anarray[j]);
        qrjson.badgeImg=bdgImg.replace("data:image","dataimage").replace(";base64,","base64");
        anarray[j]=JSON.stringify(qrjson);  
     } // End of for-loop



    toReq();
   });

Function Definition

function savebadge(){

for(var j=0;j<anarray.length;j++)
{
html2canvas($("#bdg"+j+""), {
    onrendered: function(canvas) {
        theCanvas = canvas;
        var base64img = canvas.toDataURL();
        badgeimg=base64img.replace("png","jpeg");
        alert($("#name").text());
        //console.log("render "+badgeimg);
        localStorage.setItem("bdgImg",badgeimg); 

        var img = $("<img>",{
            "src" : badgeimg,
            "alt" : "badgeimg"
        });
        $("#divimg").append(img);


    }       
});
}}