Callback help

Thanks for that advice @oesterle. I've had a go and I think it's improved but I can't close the wifi connection. wifi.disconnect() isn't recognised.

Serial1.setup(115200, { rx: B7, tx : B6 });

I2C3.setup({sda:B4,scl:A8});
var bh=require("BH1750").connect(I2C3);

var dht = require("DHT11").connect(B5);

function read_sensors(callback) {
  var n=0,i=100;
  while (i--) n+=analogRead(A7);
  bh.start(3);
  light_intensity = Math.round(bh.read()).toString();
  soil_moisture = (100-Math.round(n)).toString();
  dht.read(function (a) { 
    temp = a.temp.toString();
    humidity = a.rh.toString();
    callback (light_intensity, soil_moisture, temp, humidity);
  });
}

function send(l,m,t,h) {
  wifi = require("ESP8266WiFi_0v25").connect(Seri­al1, function(err) {  
    if (err) throw err;
    wifi.connect("Xxx", "xxx", function(err) {
      if (err) throw err;
      LED2.set();
      sendForm(l,m,t,h);
    });
  });
}

function onInit() {
  USB.setConsole(1);
  clearInterval();
  setInterval(function() {
    read_sensors(send);
  },30000);
}