javascript - 如何连续调用一个函数

Question

我希望能够连续运行这段代码，以便我调用的函数始终检查输入的是真还是假

索引.js

io.on('connection', function(socket) {
var entered = require('./main.js').onProximityBoolean; /// i want this to continuously be checking itself
   if (entered == true) {
     socket.emit('enterProximity');
   }
}

主要.js

var enter = false;
function onProximityBoolean(enter) {
  if (enter === true) {
    console.log(enter);
    return true;
  } else {
    return false;
  }
}

function isWithinBounds() {
  //inside here is sensor code that says if the object comes close 
  //then enter will be true else enter will be false
  //this part accurately redefines the onProximityBoolean
}
module.exports = {
  onProximityBoolean: onProximityBoolean(enter)
};

Answer 1

你可能想用 setter/getter 实现一个观察者:

"main.js";
var state=false;
var handlers=[];
module.exports={
  get proximityBoolean(){
     return state;
  },
  set proximityBoolean(value){
     if(value!==state){
       state=value;
       handlers.forEach(func=>func(value));
  },
  observe(func){
    handlers.push(func);
  }
}

所以你可以这样做:

var main = require('./main.js');
io.on('connection', function(socket) {
 main.observe(function(entered){
  if (entered == true) {
    socket.emit('enterProximity');
   }
  });
}

//trigger it somewhen
main.proximityBoolean=true;

---

或者使用 setInterval 定期检查:

var main=require('./main.js');
io.on('connection', function(socket){
 setInterval(function() {
  var entered = main.onProximityBoolean;
  if (entered == true) {
     socket.emit('enterProximity');
   } 
},1000);
});