This link helped me to solve my problem.
My mistake was that i was not using object details properly. Through this link I just bound the details in an object and used them. After executing loop each time value of i increase and then it take object from that position of my array and use its details. Let me show you my working code. I hope it will help someone else.
for (var i=0; i<frontarray.length;i++)
{
var objRef = frontarray[i];
var url = objRef.url;
fabric.Image.fromURL(url, function(img) {
canvas.add(img).renderAll();
}, {
id: objRef.id,
num: objRef.num,
left: objRef.left,
top: objRef.top,
angle: objRef.angle,
scaleX: objRef.scalex,
scaleY: objRef.scaley,
flipX: objRef.flipx,
flipY: objRef.flipy,
});
}