stringify

function stringify(o){
	var visited = [];
	var q = [{type: typeof o, target: o}];
	var res = '';
	var t;
	while(t=q.shift()){
		var tar = t.target;
		if(!tar){
			res += 'null';
			continue;
		}
		switch (t.type){
			case 'object':
				if(visited.indexOf(tar)!==-1){
					if(t.pos==null)
						throw new Error();
				}else {
					visited.push(tar);
				}
				t.pos==null&&(t.pos=-1);
				var pos = t.pos;
				var key;
				if(Array.isArray(tar)){
					if(pos===-1){
						res += '[';
						t.pos++;
						q.unshift(t);
						continue;
					}
					if(pos === tar.length){
						res += ']';
						t.pos =-1;
						continue;
					}
					key = pos;
					res += pos?',':'';
				}else {
					var keys = t.keys||(t.keys = Object.keys(tar));
					if(pos===-1){
						res += '{';
						t.pos++;
						q.unshift(t);
						continue;
					}
					if(pos === keys.length){
						res += '}';
						t.pos = -1;
						continue;
					}
					key = keys[pos];
					res += (pos?',':'')+key+':';
				}
				t.pos++;
				q.unshift(t);
				q.unshift({type: typeof t.target[key], target: t.target[key]});
				break;
			case 'number':
				res += tar;
				break;
			case 'string':
				res += '"'+tar.replace(/"/g,'\\"')+'"';
				break;
			default:
				res += 'null';
				break;

		}	
	}
	return res;	
}