Trying to stringify an object to JSON, but not enough memory to fit the whole thing in memory

function getTypedHistString(tdx) {
	var ret="";
	var typen = htypes[tdx];
	if (tdx<4){
		var tstr="[";
		for (var i=0;i<48;i++) {
			tstr=tstr+HISTORY[typen][i].toFixed(1);
			if (i !=47) {
				tstr+=",";
			} 
		}
		tstr+="]";
		return tstr;
	} else {
		return JSON.stringify(HISTORY[typen]);
	}
}


function processrequest(req, res) {
	try {
		var par=url.parse(req.url,true);
		var q=par.query; 
		var path=par.pathname; 
		path=path.split('/');
		path=path[1];
		switch(path) {
			case "status.json":
			var r='{"lamp":{';
			for (var i=0;i<5;i++) {
				r+='"'+colors.substr(i*4,4)+'":'+STATUS.LEDs[i].toFixed(2);
				if (i<4) {r+=",";}
			}
			r+='},\n"sensors":{"RH":'+STATUS.RH.toFixed(1)+',"Temp":'+STATUS.Temp.toFixed(1)+',"Pressure":'+STATUS.Pressure.toFixed(2)+',"Air Quality":'+STATUS.AirQual.toFixed(2)+'},\n"Light":'+JSON.stringify(STATUS.Light)+'}';
			res.writeHead(200,head);
			res.write(r);
			res.end();
			break;
			case "history.json":
			res.writeHead(200,head);
			var n=0;
			res.on('drain',function(){
				res.write('"'+htypes[n]+'"');
				res.write(":");
				res.write(getTypedHistString(n++));
				if (n==8) {res.end("}");} else {res.write(',\r\n');}
			});
			res.write("{");
			break;
			case "usermsg.cmd":
			if (query.msg && query.msg.length > 1) {
				usrmsg=query.msg;
				MnuS=10;
				setTimeout("uplcd();",100);
				res.writeHead(200,head);
				res.write("{status:\"ok\",message:\""+query.msg+"\"}");
			} else {
				res.writeHead(400,head);
				res.write("{status:\"error\",error:\"No message supplied\"}");
			}
			res.end();
			break;
			case "lamp.cmd":
			STATUS.LEDs[0]=q.BLUE===undefined ? 0:E.clip(q.BLUE,0,1);
			STATUS.LEDs[1]=q.COOL===undefined ? 0:E.clip(q.COOL,0,1);
			STATUS.LEDs[2]=q.WARM===undefined ? 0:E.clip(q.WARM,0,1);
			STATUS.LEDs[3]=q.YELL===undefined ? 0:E.clip(q.YELL,0,1);
			STATUS.LEDs[4]=q.RED===undefined ? 0:E.clip(q.RED,0,1);
			setTimeout("upled();",100);
			res.writeHead(200,head);
			res.write("{status:\"ok\",message:\"lamp state set\"}");
			res.end();
			break;
			case "code.run": //This is why I don't expose this board to requests from outside the LAN ;-) 
			if (query.code) {
				var x="";
				try {
					x=eval(query.code);
					res.writeHead(200,head);
					res.write("{status:\"ok\",result:\""+x+"\"}");
				}
				catch (err) {
					res.writeHead(500,head);
					res.write("{status:\"error\",error:\""+err.message+"\"}");
				}
			} else {
				res.writeHead(400,head);
				res.write("{status:\"error\",error:\"No code supplied.\"}");
			}
			res.end();
			break;
			default:
			res.writeHead(404,head);
			res.write("{status:\"error\",error:\"unknown command\"}");
			res.end();
		}
	}
	catch (err){
		res.writeHead(500,head);
		res.write("{status:\"error\",error:\""+err.message+"\"}");
		res.end();
	}
}

Works like a charm!

I was thinking about the object.keys() approach - but I don't want to bite myself in the ass if I later add something to HISTORY object, since my code (as you can see) makes assumptions about which index number corresponds to which kind of data, since I have to do float arrays differently from integer arrays.