javascript - 如何检查回调是否待处理？

Question

我正在学习 JavaScript，并有任务编写一个公共(public)函数来检查是否进行了异步调用，但响应仍处于待处理状态(即进程正在“运行”)。如果该过程正在进行，则需要返回 true；如果没有，则需要返回 false。

function Machine() {
  function onReady() {
    alert( 'ready!' );
  }
  this.setOnReady = function(newOnReady) {
    onReady = newOnReady;
  };
  this.run = function() {
    setTimeout(function() {
      onReady();
    }, 10000);
  };
}

 var machine = new Machine();
 alert('before the run: ' + machine.isRunning()); // before: false
 machine.run();
 alert('is running: ' + machine.isRunning()); // is running: true
 machine.setOnReady(function() {
     alert("after: " + machine.isRunning()); // after: false
 });

Answer 1

以下是编码方法:

function Machine() {
  // add this private variable
  var isRunning = false;
  function onReady() {
    alert( 'ready!' );
  }
  this.setOnReady = function(newOnReady) {
    onReady = newOnReady;
  };
  this.run = function() {
    isRunning = true; // set flag
    setTimeout(function() {
      isRunning = false; //clear flag
      onReady();
    }, 2000); // 2 seconds, I don't have patience!
  };
  // Add this method:
  this.isRunning = function() {
    return isRunning;
  }
}

var machine = new Machine();
console.log('before the run: ' + machine.isRunning()); // before: false
machine.run();
console.log('is running: ' + machine.isRunning()); // is running: true
machine.setOnReady(function() {
  console.log("after: " + machine.isRunning()); // after: false
});