Thanks Rob for always being helpful. I am using simple math to get bbox from lat,long. It is not accurate for closest zoom scale.
var minxx = lon - 0.08999;
var maxxx = lon + 0.08999;
var minyy = lat - 0.08999;
var maxyy = lat - 0.08999;
console.log("weblink/bbox?" + "xmin=" + minxx + "&ymin=" + minyy + "&xmax=" + maxxx + "&ymax=" + maxyy).
I have WGS-84 projection. Do I have to add condition for each scale. e.g.
If (scale =11)
var minxx = lon - 0.08999;
var maxxx = lon + 0.08999;
var minyy = lat - 0.08999;
var maxyy = lat - 0.08999;
elseif (scale =19)
var minxx = lon - ??;
var maxxx = lon + ??;
var minyy = lat - ??;
var maxyy = lat - ??;