while 循环不会爆发

Question

做一个练习，我不知道为什么我的 while 循环没有转义，它一直说即使只输入数字，这些值也是无效的。有什么想法吗？

// 31. Karvonen Heart Rate
var age, restingPulse, targetRate, numCheckAge, numCheckPulse, valid;
    
    valid = false;
    numCheckAge = /^\d+$/.test(age);
    numCheckPulse = /^\d+$/.test(restingPulse);
    
    while(valid === false) {
      age = parseFloat(prompt("Enter your age:"));
      restingPulse = parseFloat(prompt("Enter your resting heart rate:"));
      if(numCheckAge === true && numCheckPulse === true) {
        valid = true;
      } else {
        alert("Sorry. That's not a valid input, please enter numbers.");
      }
    }
    
    for (var i = 0.55; i < 1; i+=0.05){
      targetRate = (((220 - age) - restingPulse) * i) + restingPulse;
      document.write("Intensity: " + Math.round((i * 100)) + "% | Rate: " + Math.round(targetRate) + "<br>");
    }

Answer 1

我已经简化和灵活了你的代码；）

看看这个：

    
function requireNumericPrompt(text) {
  var value;
  while(true) {
    if(/^\d+$/.test(value = prompt(text))) {
      return value;
    }
    alert("Sorry. Please enter valid (numeric) value.");
  }
}

var age = parseInt(requireNumericPrompt("Enter your age:"));
var restingPulse = parseInt(requireNumericPrompt("Enter your resting heart rate:"));

document.write('Age: ' + age + '<br/>');
document.write('Resting pulse: ' + restingPulse + '<br/>');
for (var targetRate, i = 0.55; i < 1; i+=0.05){
  targetRate = (((220 - age) - restingPulse) * i) + restingPulse;
  document.write("Intensity: " + Math.round((i * 100)) + "% | Rate: " + Math.round(targetRate) + "<br>");
}

Answer 2

在您测试正则表达式时，这些变量age 和restingPulse 是undefined。您必须将用于测试的代码移到循环内， 这些变量从用户输入接收到值：

while(!valid) {
  age = parseFloat(prompt("Enter your age:"));
  restingPulse = parseFloat(prompt("Enter your resting heart rate:"));

  numCheckAge = /^\d+$/.test(age);
  numCheckPulse = /^\d+$/.test(restingPulse);
  if(numCheckAge && numCheckPulse) {
    valid = true;
  } 
  else {
    alert("Sorry. That's not a valid input, please enter numbers.");
  }
} 

也可以去掉=== true位，直接用变量的真值进行测试。

Answer 3

var age, restingPulse, targetRate, numCheckAge, numCheckPulse, valid;

valid = false;
numCheckAge =function(a) { 
	return /^\d+$/.test(a);
}
numCheckPulse = function(a){
 return /^\d+$/.test(restingPulse);
} 

while(valid === false) {
  age = parseFloat(prompt("Enter your age:"));
  restingPulse = parseFloat(prompt("Enter your resting heart rate:"));
  if(numCheckAge(age) && numCheckPulse(restingPulse)) {
    valid = true;
  } else {
    alert("Sorry. That's not a valid input, please enter numbers.");
  }
}

for (var i = 0.55; i < 1; i+=0.05){
  targetRate = (((220 - age) - restingPulse) * i) + restingPulse;
  document.write("Intensity: " + Math.round((i * 100)) + "% | Rate: " + Math.round(targetRate) + "<br>");
}

您需要将检查代码转换为函数而不是变量。

Answer 4

您在正确的轨道上只是忘记初始化变量。

var age, restingPulse, targetRate, numCheckAge, numCheckPulse, valid;

age = 0;
restingPulse = 0;

valid = false;
numCheckAge = /^\d+$/.test(age);
numCheckPulse = /^\d+$/.test(restingPulse);

while(valid !== true) {
    age = parseFloat(prompt("Enter your age:"));
    restingPulse = parseFloat(prompt("Enter your resting heart rate:"));
    if(numCheckAge === true && numCheckPulse === true) {
        valid = true;
    } else {
        alert("Sorry. That's not a valid input, please enter numbers.");
    }
}

for (var i = 0.55; i < 1; i+=0.05){
    targetRate = (((220 - age) - restingPulse) * i) + restingPulse;
    document.write("Intensity: " + Math.round((i * 100)) + "% | Rate: " + Math.round(targetRate) + "<br>");
}