javascript json转换为string

function obj2str(o){
var r = [];
if(typeof o == "string" || o == null) {
return o;
}
if(typeof o == "object"){
if(!o.sort){
r[0]="{"
for(var i in o){
r[r.length]=i;
r[r.length]=":";
r[r.length]=obj2str(o[i]);
r[r.length]=",";
}
r[r.length-1]="}"
}else{
r[0]="["
for(var i =0;i<o.length;i++){
r[r.length]=obj2str(o[i]);
r[r.length]=",";
}
r[r.length-1]="]"
}
return r.join("");
}
return o.toString();
}